Electrical Hints And Problems
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electricalhints.htm
15
I recommend purchase of either a
test lamp; or, a
multi-meter that will fit in your tool tray on the bike.
Some people have both, but a simple test lamp can be very helpful
in tracing down problems. A meter is NOT a necessity
for an on-bike tool. If you purchase a test lamp get one with a hardened steel
pointy tip, NO battery, and a stranded insulated wire with an
alligator clip (if that wire is not at least 4 feet long,
lengthen it).
Which multi-meter? (BTW...'multi' means Multiple Function)
Any inexpensive digital meter is likely going to be OK, but
read about them here before you purchase!
One very small digital meter that I recommend ONLY for the
on-bike tool tray (IF you decide to get a meter to carry with
you) is the Radio Shack FOLDING miniature LCD digital auto-ranging multi-meter.
Probably model number 22-802 (previously 22-179a). This small and
accurate meter, which includes a diode test function, comes
complete with built-in test leads in a small case (which can NOT
be left in bright sunlight too long, or it deforms). It is
nice to add a pair of tiny alligator
push-ons, which WILL fit inside the case. Check its
batteries once every year or two. Be SURE you
understand how to use the meter. It would be a good idea to
make up two jumper wires, insulated stranded conductor type,
perhaps 6 feet long, with medium size alligator clips at each
end.
If you are purchasing a meter for your at-home use, or you have
lots of room on your bike, then I recommend a larger one, making
sure it has a diode test function, and at least a 10 ampere D.C.
function. You need only have the type of meter called
"3-1/2 digits". There are cheap multi-meters that measure
ohms, DC volts, AC volts, DC current, diode test, and some
automotive types include other functions. I
have seen many of these various types of digital multi-meters
selling for UNDER $30. There are some that cost
a bit more, and have a CLAMPING action to measure A.C. current.
Nice tools.
There are digital and analog meters sold. Analog
meters have their uses, but I recommend a digital type, as they
are vastly more useful for measuring precisely such things as
your bike's electrical system regulating voltage.
Some pricey
multi-meters, on the ohms function,
will not 'turn on' diodes and thereby cannot test diodes
properly. Before purchasing a meter,
unless there is
a separate diode function on the meter, always test the
multi-meter
with a diode (the place selling the meters undoubtedly has diodes
around), on the ohms range. If the multi-meter has multiple ohms
ranges, the lowest one is usually the correct one for diode
testing.
HINT! Try testing a diode on both the diode test
function (if it has one) of your multi-meter, and the ohms
function. Typically, on a diode function, the
multi-meter will read out the forward voltage of the diode; and
in reverse connection, nothing. On the low-ohms range, the
meter will read the forward resistance of the diode, and on
higher ohms ranges with leads reversed, it will read near
infinity. Thus you test the forward and reverse function of
the diode, by either test.
A typical small power diode will read roughly 0.6 volt in the
diode test in the forward direction; and on the low ohms scale it
might read anyplace between 8 ohms to 100 ohms....each meter is
different. For the nerdy types, I recommend you find out
what your meter reads; and remember that.

I recommend you make up
a special jumper wire; use insulated stranded conductor wire, and
attach standard 1/4th inch male
push-on connectors at each end. Make this jumper about 4 to 6
inches long. Put it in your ON-BIKE
tool kit. Its purpose is to allow bypassing of the Voltage
Regulator; for testing, or, if the VR fails.
Bi-yearly maintenance of your electrical system is a very
good idea. You should remove plugs, clean contacts,
and use a contact cleaner, perhaps after mild abrasive techniques, perhaps
use a clear silicone grease or spray silicon oil to protect against atmospheric effects
like corrosion. There are premium contact oxidation
prevention products on the market, the best are probably made by
Caig Laboratories. Caig's products are highly
recommended by me; particularly for sensitive areas, such as K
bike computer pins; but they are excellent for any electrical
connection that might corrode from atmospheric effects.
Measurements of voltage can be taken
on your airhead with various items turned on or off, such as the
headlight. Except for the heated grips circuits, voltage drops of over 1/4 volt in any
wire or
switch or across contacts will indicate that there is a problem.
When measuring voltage drops, you
will get a more accurate reading by
connecting the multi-meter + (positive) lead to the battery + terminal, and
using the multi-meter - (negative) lead as the test prod.
Doing it this way means that you need not subtract voltages from
each other; as you get a direct reading of voltage drop.
Be sure that your
Airhead's brown wires (grounds, earth, chassis, battery -.....) are
secure everyplace. There are places that are known
problem areas, such as the front coil mount and grounding wire(s)
on the R65 early models....due to cracked mounts.
****SPECIAL NOTE!!!: In some repair manuals, it is wrongly said, or wrongly implied, that you can use a voltmeter connected in a series connection, to measure such as diode leakage, or current drains, etc. Some imply that connecting a VOLTmeter between the battery negative terminal and the chassis, will allow leakage measurements. This is absolutely NOT TRUE. You use a ammeter, or milliamp-meter function, for this.
NUMBERED HINTS, ADVICE, TECHNICAL STUFF, ETC!
1. VERY FEW OF YOU WILL EVER
REPLACE INDIVIDUAL DIODE BOARD DIODES.
However, the information in this section covers lots more than
that...so read it fully!
The large power diodes (which are pressed-in-place) used in
the diode boards are Motorola 1N3659 (cathode to case) and
1N3659R (anode to case). There may well be other
manufacturer's numbers that will fit there; and you are LIKELY to
NOT see these Motorola part numbers. Three
of each type of power diodes are used. No matter
whose make of diodes are used, the top row are the same part
number, and the bottom row are the other part number; and the
difference is that the diode polarities are reversed from each
other. They
are all rated at 50 volts, and 30 amperes at 100°
C. Some alternator repair shops may stock
similar diodes. Generally any diode rated at 30 amperes or
more, that will fit, will work just fine. AGAIN!...MIND THE
POLARITY...all 6 are NOT the same! You may use
higher rated diodes such as the 1N3660 and 1N3660R (100 volts) or
1N3661 and 1N3661R (200 volts); or, as mentioned, most alternator
repair shops have diodes that will work OK. Be careful pressing them in
and out.
The solid wire from these diodes SHOULD BE FOLDED OVER and soldered along the length of that FOLD, onto
the printed circuit board. If need be, scraping away (or use paint remover)
the coating over the copper on the board, to gain an adequate
soldering area, before soldering.
This folding over and soldering was especially critical on the
hotter-running RS/RT faired models, the original Werhle
manufactured boards failed due to that problem (of not being
folded over). It is better to use a 50-50
solder, adding rosin flux, rather than 60-40 electronics solder.
50-50 melts at a considerably higher temperature and holds up
better in THIS application. Plumbers wire solder is usually
50-50. Be sure to use rosin flux (plumbers solder usually
has no
flux core). If your large diodes on the diode board are
showing signs of heat distress at the solder joint of that diode
wire to the PC board then they need re-soldering (even if already folded). IF the wire is NOT folded over, you CAN use 50-50 solder
which has worked for me; but,
the BEST fix is to drill a tiny hole through the copper printing
material, and add a piece of wire, folding it over and soldering
it to the PC, and also under the board, have it tightly wrapped
and then soldered on the diode lead (clean well first or it will
not solder correctly). That job, for all 6 diodes, is
QUITE a bit of a problem for many of you, trying to get the soldering iron underneath
the printed circuit board. I have gotten decent results by
cleaning the soldering area pad and using 50-50 solder, on the
'bad' boards that come without folded-over leads.
If you are
going to test the diode board a visual inspection, especially
the solder joints, is the first thing to do.
Then use an ohmmeter (or
diode test meter function) that produces enough voltage/current
to turn on the diodes in the forward direction, and thus check
the forward diode function. Reverse the leads and also
check the reverse diode resistance. The forward resistance or
diode tester readout (which may be in voltage) is very low
compared to the resistance in the reverse direction.
DO NOT have the battery of the motorcycle connected when testing
the diode board in the bike. All
the diodes should be roughly the same. Anal types can
repeat the tests when the board is heated to approximately
200°F.
The best diode test is with a transformer that supplies ~5 to ~15 volts AC, connected in series with a brake lamp or turn signal lamp (not a small lamp of lesser current drain), and the diode tested in this series circuit. Full brightness is shorted diode, half brightness is proper, no lamp illumination at all is an open diode. You can modify an old high intensity desk lamp that has a lamp and transformer, or make up something else. The June 1999 issue of AIRMAIL has a long article on diode boards by OAK. A separate article on diode boards and their grounding wires, etc. is on this website: Diode boards
NOTE! It is perfectly acceptable to use an application...or two or three....of any common gel type paint remover product...on the outer diode board printed board....to enable removal of that pesky paint coating. You do not have to re-apply paint later. If using paint remover, use a water dampened cloth to remove the excess and then clean the board soldering area to shiny condition, before doing any soldering. I use 50-50 plumber's solder, adding soldering rosin (soldering rosin is available in all hardware stores in a tiny can, it helps clean and prepare the joint as you solder), to make a stronger joint. DO NOT use common electronics solder, which is typically 60-40. Removing the coating will enable easy soldering of the diodes. One of the indications of problems is when the solder joints at the 6 large diodes is discoloring and otherwise deteriorating upon a simple visual inspection ...the board need not even be removed to see this...it is right in front of you with the aluminum cover removed. FIX those joints! Be sure the battery is disconnected! Use an adequate sized soldering iron. Even a low power iron can work OK, if the iron tip is massive.
2.
****CRITICAL ITEM****!!!
Unless you
have an aftermarket EnDuralast Alternator...NEVER remove
the outer timing chest cover without first
disconnecting any and all leads at
the battery negative terminal. IF
you have ONLY the large diameter
black battery negative lead at the battery negative, then you CAN
disconnect at the speedometer cable hollow bolt, and there is no
need to unfasten that heavy wire at the battery
negative. If you have other wires at the battery
negative post (at the battery itself), you should disconnect all of
them at the battery negative, so as to be SURE there is no
grounding going on, such as through a power jack,
etc. Failure to heed this hint
can result in ruining a diode board during removal of the
outer timing chest cover. The accessory
jack may be grounded in its mounting, and may not be, depends on
model you use. Anything that provides an alternative
grounding for the battery is suspect. Safest ground for
'such things' is back to the frame, not the battery negative; so
keep that in mind when installing accessories.
NOTE that the original plastic cover for
the BMW accessory jack was 1 piece rubber or plastic and eventually broke from flexing. You can replace it with the pricier, but far
better cap from a K model, and the part is:
61-12-2-303-574. There are other jacks, of course, that
work fine. Just be aware of the possibility of a JACK
grounding problem.
At the hollow speedometer cable bolt, disconnecting is made easier by clipping, filing, or cutting the lug, so it JUST fits OVER the screw, so the screw does not need removal, only loosening. Be sure the washers are there. That hollow bolt is modestly fragile, don't over-tighten, and be sure it has the the two flat washers.. If one is a waverly washer or lock washer, that will ensure there is no need to excessively tighten. Just barely snug with a 10 mm short wrench is all the tightness that is needed here.
3. Starter circuitry, basic: the /5 bikes, and ONLY the /5 bikes, have a different type of starter relay (and an additional function) from all of the rest of the later Airheads. In the Slash 5, once the engine starts, the rising alternator output is used to prevent the starter relay from being accidentally operated. The original stock /5 relay had a problem, that could cause one to think the battery was bad or failing. The /5 relay has a very simple transistor circuit inside. It has a faulty design. In cold weather, and/or sometimes with just a slightly weak battery, the transistor fails to operate correctly (its 'gain' is greatly reduced), and the relay will vibrate slowly rather than stay pulled-in, when the starter button is actuated. This results in a noise called 'the cricket'. "Oak" Okleshen coined that name, Cricket, in the early 70's. ... and of course the fix is called 'The Cricket Fix'. The sound of the Cricket is sort of a clackety-clackety at a fairly fast rate. Both that starter relay....and usually the large solenoid relay on the starter motor,... are doing the clackety dance together. The result is no starter cranking function, just the noise, and is very similar to what one might expect with a near dead or very low charge in a battery in a car. The proper fix is to remove the /5 relay (located in a metal can, left side of frame backbone under the fuel tank, and is the furthest forward item), open it up, and make a few simple changes. There is a complete illustrated article on a permanent fix for the relay on this website at: slash5cricket.htm which is article 37. I still see them once in a great while that were never modified. I HIGHLY recommend this fix be done; even if you have not yet experienced any problems.
After
the /5, the starter circuitry was changed, the anti-start
function in the /5 was eliminated. In the later models the relay
is used strictly as
a low power relay to drive the starter motor solenoid.
Later models had a neutral switch that did more than illuminate a
lamp, and BMW added starting complexities
tied to that later neutral switch and also added a clutch switch
on the handlebars that tied into the new circuitry. There
are variations on the actual circuitry used on the later models.
In any discussion that follows for
the bikes after the /5, it is assumed that the KILL SWITCH is in
the RUN position. If it is not, no power goes to the
starter relay engaging circuitry. After the /5, the starter relay circuitry is
arranged such that the starter cannot be engaged if
the bike is in a gear and the clutch
lever is out.
NOTE: it is possible to use a common ordinary auto-parts
store relay to substitute for the /5 starter relay, if you
understand what to do....the anti-start function is gone,
however....but the /5 will operate like the later bikes (but no
special neutral switch nor clutch switch functions...see below).
The starter relay on the /6 and
later can be substituted by commonly available relays, but some
relays in the BMW have a diode, so I don't recommend this unless
you understand what is going on with YOUR relay and bike.
Use of the proper BMW relay allows the proper function of the
neutral lamp. The starter relay is usually repairable. There is a very extensive article
on relays in the Technical Tips section of the Airheads Club
website:
http://www.airheads.org
NOTE that the position of the starter relay varies by model and
year. Rather than make a listing of all the variations,
here is a simple way of determining which is the starter relay
(there are other ways). If the right side of the top frame tube has TWO
relays side by side (left to right) at the rearmost, then the
starter relay is the one closest to the tube, and the headlight
relay is the one to its right. If the top frame tube has
ONE relay at the rear most, then that relay is the headlight
relay and the relay in front of it is the flasher, and the relay
to the right of the flasher is the starter relay.
***NOTE!: There is a peculiarity of the starter relay on the /6 and later models. I think it was done for some sort of electrical disconnect function during factory checkout following production of the motorcycle. The starter relay, under the tank (but can now be in several positions on either side of the frame backbone), has been known to get corroded male-female plug-in connections. The peculiarity is that 100% of all electrical energy for the motorcycle (except for the large gauge wire that feeds the starter motor solenoid/starter motor) goes through a JUMPER built INSIDE the starter relay. You can loose part or all of the electrical energy for the bike if there is corrosion at the relay or its socket. Wiggling the relay or unplugging and re-plugging it will usually return power. To fix properly, clean the male and female spades carefully, and THEN add silicone grease; or, a high quality protectant from such as CAIG Labs; before pushing the relay back into its socket. NOTE that if the starter relay is warped by using excessive force during removal, it may twist the relay internal parts just enough to actually close the internal relay contacts, and fire up the starter motor!
Here is another way of stating some of this...and more...
Beginning with the /6 airheads, BMW changed the wiring at the starter relay. There are two wires leading from the battery + terminal into the airhead electrical system. The big heavy gauge wire goes from the battery + terminal directly to the starter solenoid on the starter motor assembly. That supplies the very large current demand when the starter is operated. The alternator diode board also output feeds that point. The starter can not operate from just that wire, it needs its solenoid energized, which is done via the starter relay. A smaller gauge red wire at the battery + terminal goes to the starter relay under the gas tank. Do not mistake that wire for a possible third wire to an accessory socket or other added accessories. That smaller gauge red wire, that connects to the starter relay, connects to one of that relay's internal contacts, supplying power to the starter solenoid via its mating contact, when you press the starter button (key switch on). But, there are one or two other red wires at the relay. Usually two heavy gauge red wires and one lighter gauge red wire are what is seen at the relay plug. There is no connection between the two larger gauge of the three red wires at the relay socket, unless the relay is plugged-in. The relay does NOT have to be energized by the starter button for this....it is a design feature of the relay, metal is molded into the relay base, that jumpers one terminal 87 to another terminal 87. There are some minor variations over the years and models, but this is basically what happens to the two larger gauge red wires at that relay....they are connected when the relay is plugged-in. My suspicion is that BMW did this for some production line purpose. If corrosion or poor contacts are present at the plug/relay terminals, there will be some voltage drop at those connections. It HAS happened that a total electrical failure has occurred from such corrosion. In the past, as above, I have recommended that the relay be at least plugged in and unplugged, several times, and silicone-greased on the connections to help with some weather protection. Other recommendations from me have included doing a painstaking cleaning of the contacts. "Painstaking" because the female socket connections are hard to clean.
4. Varies problems,
descriptions, etc., for 'funny things' with neutral lights,
clutch switch functions; etc. Pesky Diode Problems!!
A. This applies to models
after the /5, that have a neutral light ON when the
transmission is in any gear, and that light is OFF in
neutral. A common cause is poor contacts in the
umbilical cable plug that fits into the back of the instrument
pod. Clean them. Just why this can
happen, which is fairly rare, is unimportant to try to explain
here.
B. On a /6 and later bike, if the neutral lamp seems to function normally for neutral and normally for any gear other than neutral...BUT...if you are in a gear, and the neutral lamp comes on when the clutch bar lever is pulled backwards, then a diode has shorted. If that diode opens, there will be no starting in neutral, UNLESS the bar clutch lever is pulled back, as the diode is effectively not there to allow current flow through the neutral switch. The purpose of this diode is to prevent the neutral light from being on when in a gear and the clutch is pulled in. In the twin rear shock airheads, except R45/R65, the faulty diode is to be found HIDDEN on the backside of the board inside the headlight area. Pre-1981 R45/R65 have the diode in the wiring below the starter relay area, and post 1981 R45/R65, and all Monoshock models, have the diode within the starter relay. SEE #5. The diode under discussion can short, or it can open, as described above. There were a LOT of variations on the starter diode and associated circuitry over the years of airhead production...perhaps as many as 6 or 7 versions.
C. The starter circuits vary with year and model. In
ALL models, the starter solenoid, a huge relay-switch itself,
is wired directly via a BIG wire to the Battery + terminal. A
much smaller 'starter-relay' is under the tank; the purpose of
the small starter relay is to allow a small switch, the on-bars
push-button, to operate a huge powerful and current demanding
relay (the solenoid relay), via the starter relay contacts.
There are differences in the various
airheads are in how the starter relay and its circuitry are connected and wired.
D. In a /6, assuming it is stock, the power to run the starter
relay begins at the battery + terminal, goes to the ignition
switch, then to the KILL switch on the bars, and then to TWO
different but somewhat connected circuits. The
#1 circuit is the starter relay COIL + side. The + power
goes through that coil, and the - side of the coil has the clutch
switch in it, the + power goes through that clutch switch, to
ground (assuming the switch is functional, shorted, with the
lever at the bars pulled backwards). This is why a
bike should always start if the clutch lever is pulled
backwards. If a bike does not, then the bars clutch switch
or connections are faulty. The #2 circuit is actually
TWO parts:
part a: the neutral indicator green lamp
portion. There is another connection from the + output of
that above mentioned KILL switch. This
connection goes to the
neutral lamp. The lamp's other side goes to the neutral
switch. Anytime the ignition and KILL switch are in the ON
and RUN positions, and the neutral switch CLOSED (which it is
supposed to be, in the N position of the transmission), the lamp
lights up.
part b: This is a bit complicated, so follow through
with me here. I previously explained that the power went through the starter relay coil
and then to the clutch switch. At the clutch switch connection
(or, - side of the relay coil, which is the same thing), a diode
is connected.
That diode is connected to the transmission
neutral switch. The actual purpose of the diode is to BLOCK flow
of current from the N
indicator lamp to the clutch switch.
You don't want the lamp turning on just because you are pulling
in the clutch, rather, you want the
lamp on only in neutral. A
diode is a one-way device when it works correctly.
TWO things happen if this diode fails. If it "opens", then the neutral switch
has no effect on starter operation, and the neutral switch does
NOTHING but illuminate the lamp...it does NOT allow starting in
neutral withOUT the clutch pulled in. The bike is supposed
to be startable in any gear, or neutral, if the clutch is pulled
in, and is supposed to be startable anytime the transmission is
in neutral. If the diode shorts, the neutral lamp will
illuminate EVERY time the clutch is pulled backwards. The
bike will also start in neutral. NOTE THESE SYMPTOMS.
I will ASSUME that you have a failed diode. What to do?
The diode on a /6 bike should be located UNDERNEATH
the circuit board in the headlight shell. It is not easy to get to. If shorted, it MUST be disconnected,
although you can install the new diode above the board. What type
of diode? You can use just about any
silicon power diode rated at 1 ampere, but I prefer to use one rated
at 2-1/2 or 3 amperes. Any voltage rating on the diode is
acceptable, as they are not made in under 50 volts.
A diode rated at 50, 100, 200, 400, or even 1000 volts, is
perfectly acceptable. Radio Shack sells them in small packages rather cheaply. Usually more than one
diode (typically 2) per package. Keep the other diode(s) to experiment with; perhaps
on your ohmmeter, to see how it tests diodes. You MUST install
the new diode with the LINE marking on one end of the diode in
the SAME direction/position as originally installed. You won't
burn anything out if you do not, but the proper functions will
not be had. The line is officially called the
'cathode'. Once in awhile diodes come with the line and an
arrow pointing and touching it.
Be sure to read #5 below!
Nerdy comment: + current
applied to the NON-line end, will go THROUGH the diode, but not
if the applied current was negative to the NON-line end.
5. In the 1985 and later (but NOT including the GS
and the 1985 R65), the starter BUTTON and starter relay COIL
circuitry were CHANGED. That starter relay (under the
fuel tank, along the backbone) now contains the diode mentioned
in #4 above. The
starter button is on the PLUS (+)
side of the relay coil instead of the minus side. Thus, BMW could
now mount the diode INside the relay.
This makes for a difference in troubleshooting.
NOTE that the position of the starter relay
varies by model and year. Rather than make a listing of all
the variations, here is a simple way of determining which is the
starter relay (there are other ways). If the right side of the top frame tube has TWO
relays side by side (left to right) at the rearmost, then the
starter relay is the one closest to the tube, and the headlight
relay is the one to its right. If the top frame tube has
ONE relay at the rear most, then that relay is the headlight
relay and the relay in front of it is the flasher, and the relay
to the right of the flasher is the starter relay.
Here is a circuit description for these later
models, since the basic operation is somewhat similar, no matter
the circuitry:
When you turn on your ignition switch,
the battery positive (+) is connected to both the neutral light
and to the starter button. In order for the starter to
operate, that starter button then sends, if pressed, voltage to
the starter relay coil. The other side of that relay coil DOES
NOT go directly to ground. Rather, it connects to TWO
places.
It connects to the CLUTCH switch
(at the lever at the bars). This
applies to earlier models too!....if they have that switch.
It connects through the diode
(inside of the starter relay) to the NEUTRAL switch (underside of
the transmission). BOTH of these two switches, other pole,
connect to ground. Thus, if EITHER
the clutch switch or neutral switch, are grounded, the button
will operate the starter (starter relay will send power to the
solenoid on the starter motor, and activate
it). NOTE: if
you try to substitute a relay without the diode, things won't
work as intended!
NOTE: The neutral LAMP is wired such that it will ONLY turn on if the NEUTRAL switch is closed (shorted contacts, internally, due to the transmission being in neutral).
IF the diode fails by OPENING, then the neutral switch will still
operate the neutral LAMP OK, but you CANNOT operate the starter
UNLESS the clutch is pulled in.
IF your neutral lamp itself is ok, and if the circuitry to the
lamp is OK, but the LAMP is NOT being turned on and off by the
transmission being in neutral or not...then the transmission
neutral switch is faulty. Easy to determine, just short across or
open the connections at the switch on the bottom of the
transmission. Typically with a faulty switch the bike will NOT be
startable, unless the clutch is pulled. Thus you need to
determine if the lamp is operating normally, in order to decide
if you have a bad neutral switch, or a bad diode. Be advised that
you might simply have a wire pulled off the neutral switch.
The neutral switches are NOT the same,
early and late model...they LOOK somewhat the same, but a
change was made in 1976. If you have a bad one, be
SURE to get the correct one.
If you do not install the correct starter relay, you can have an open diode indication, as relays you might find someplace other than the BMW bike dealer, will not have the diode. This can happen if someone swapped with the headlight relay, it is not the same relay internally.
If you have a 1987+ Monolever bike and the lights come on with the starter in operation, there is a faulty diode inside the starter relay (2 diodes are in these models, inside the relay box). This lights on thing will then also happen in the PARKING lights position.
NOTE!
The 1974-5 neutral switches have a shorter stem. If you
install the wrong switch, things do not work
correctly! Neutral switches are CLOSED in
neutral, turning on the green neutral lamp, enabling the starter
function if the starter button is pressed. But if the
diode shorts, then the lamp is ON if the lever at the bars is
pulled. There
is a peculiarity with the 1978-80 models, which have a master
cylinder under the fuel tank.
These incorporate a float switch, whose purpose is to illuminate
the brake failure light if the fluid runs low. The lamp
gets tested each time you start the bike, via a diode. If
the diode shorts, and you are also low on fluid, the starter
could theoretically energize.
6. The headlight relay on later models has a
diode between point 86, the green or green/violet wire, and point
87b, the gray wire. The CATHODE of the diode connects to terminal
point 87b. This diode sustains the tail and instrument
lamps DURING starting...probably a German safety requirement. If
the diode shorts, the ignition will stay on, and even the key
will not shut off the engine, unless you disconnect a battery
wire...which removes the relay circuit problem instantly...but
only until the next start. This relay turns the
headlight off during cranking.
The wiring at this relay is interesting. Pin 85, the black wire, is the "to-be-grounded" side of this relay's coil, and it connects to the STARTER MOTOR. Thus, during cranking, BOTH sides of the relay coil connect to the nominal 12 volts, and the relay is NOT energized. Because of this strange, but CLEVER idea, a problem with an open starter motor, which can be intermittently open, can cause this relay to be inoperative! Thus, no headlight unless you use the high PASSING switch, which bypasses the relay...that is...it has its own wiring, separately. NOTE what I just said: The PASSING switch, that turns on the high beams, and is spring loaded to return when you remove your finger, bypasses the headlight relay...it is also unfused. THUS if you have a problem of NO headlight in High or Low beam selection switch setting, but you push that switch all the way down, for passing mode, and you DO get a headlight, then check the headlight relay. We will assume here that you have checked fuses in your bike first.
NOTE: if the relay is marked 1.244.411 then it has TWO diodes inside. I am not 100% certain of the extra diode's function. I THINK that the extra diode's function is to prevent current in the opposing direction from operating the relay. That could come about with a stuck starter solenoid (which contains two contacts). This other diode is connected so that the cathode connects to pin 85, and the anode is to the coil. From 1987, Monolever bikes had two diodes in that relay. If the lights all come on when the starter is operated .... or Park position of the switch is selected.... then one of those two diodes has shorted.
7. The charging lamp (GEN) MUST be
brightly lighted when the ignition is on, engine not running. This
lamp provides the initial alternator rotor energizing current.
DO NOT depend on the alternator to self-energize at 5000 +
rpm. IF the lamp goes out when the engine is running
(especially at say over 1500 rpm)...but there is no substantial
charging, the regulator can be checked with a little jumper wire
with spades attached...see at the top of this
article. Remove the tank, UNplug the voltage
regulator, and jumper D+ blue to DF black in the plug. DO
NOT jumper to a brown wire!! The proper jumpering
bypasses the regulator, and the light should go out around 1000
to 2000 rpm. Strong charging as rpm rises indicates a bad
voltage regulator. If the lamp was not lit at any time, and the
lamp itself and its printed circuit
connection (and no hidden cracks!) tested OK, and if the
regulator was bypassed by the jumper, and the lamp now lights up,
you probably had a faulty regulator. If you need to delve
further, you might start by measuring the voltage at the rotor
terminal...or, better yet, the slip ring itself (brushes have
been known to not make contact!). BTW: If you have a
bad regulator, you can limp home at lower than normal rpm (to
avoid overcharging the battery), with the jumper in
place. Most any three terminal regulator used in
modern cars also works.
NOTE: After the /5 (rotors about 7
to 8 ohms), rotors measure about 3 to 4 ohms, and about 2.7-3 for
the last production. If your rotor measures many tens
or higher, the rotor IS BAD (be sure it is not bad brush
contacts...measure AT the slip rings, then at the brushes).
The brushes typically add about an ohm to the rotor
reading. Rotors tend to OPEN circuit, sometimes this
happens only at some rpm, or when hot or cold. When a snail
spring bottoms-out, the brushes get intermittent. If the
snail spring has insufficient pressure, there will be poor
contact of the brushes...particularly important on the later
rotors. There is information on this site on
problems with the diode board connections that can influence
charging from tiny voltage drops: diode
boards, etc. Information on
modifying the GEN lamp circuit so that the alternator will still
operate if the lamp burns out, is filed elsewhere's on this
site: Gen
Lamp Modification
8. If
you have a GEN lamp that lights up faintly
while riding along (sometimes it is faint enough to be seen only
at night)... this is almost always due to a build up of
small amounts of poor contacts and/or corrosion, at various
places in the electrical system. It IS POSSIBLE for a
badly sulfated battery, with one or more shorted, or nearly so
cells, to cause the GEN lamp to come on, often dimly.
Electrical connections can cause that dim lamp, as can some brush
problems. If this gets bad enough for the light to
shine fairly good, you have serious connection problems
OR possibly so-so brush contacting of the slip rings.
Brushes USUALLY last about 70-80K. They will last less on bikes
ridden in dirty air or with higher electrical loads. Brushes are
best changed with the stator assembly removed.
NOTE that when at least one brush is worn far enough its snail
spring will start to bottom out on the plastic brush
housing. At that point, a tiny bit of wobble (slip ring
runout) of the rotor will cause the GEN lamp to light up
dimly...and possibly to increase that brightness as
rpm is raised. There is an article on this website
about brush
servicing.
Note 1:
When a GEN lamp does NOT light up at ignition key turn-on and
engine not running (or at idle rpm), the lamp is faulty, or the
lamp socket, wiring, regulator, brushes, or rotor is open
circuited. This is almost always very easy to figure out.
Note 2: The
GEN lamp is connected at the output of some small diodes in the
diode board, and the other side of the lamp connects to the
battery, but through the key switch. As the alternator
begins to produce current, those small diodes are SUPPOSED to
have the same exact output voltage as the large power diodes that
feed the battery more directly. Anything in either of these
two connections circuits that allows for enough voltage
difference to light the lamp will do so. Thus, a difference
could occur with a problem in the diode board, but also in any
voltage drop that was excessive at several places, including the
switch, the starter relay jumpering, etc. It is actually
possible to measure the voltage drop down the system, by using a
simple setup. You connect your digital meter positive (red
or + ) lead to the battery + terminal, and the meter negative
lead connects to various test points you are interested
in. That allows directly measuring the drop itself.
Be SURE the battery connections are very good, a KNOWN GOOD
battery, and connections from battery to transmission and to the
starter motor and to the large terminal on the right side of the
diode board, facing from the front. A known good battery is
NOT just one that will start the bike. You can measure the
battery terminal voltage, under load, such as the headlight or
during starting, that will give you some idea.
.Alternator brushes are about 16-1/2 mm long when new, measured from the middle of the concave to the top of the brush. While there have been minor changes in the brush holders over the years, a common problem is to let those brushes get too short, and then the coiled spring on the brush will bottom out on the brush holder, the brush will then have no, or hardly any, pressure against the rotor, and you will have strange charging problems. This includes often a glow from the GEN lamp, at riding speeds at night, sometimes even visible in daytime. Note that the rotor is not perfectly concentric in operation, thus as it rotates at various rpm, it can cause the brushes to bounce when they are very short and the snail spring is touching the holder. This can make for a brightening or other irregularity of the lamp as rpm rises. It is best to replace the brushes when they are around half worn, but you can let them go until the snail is almost bottoming. Information on brushes (that is a hyperlink) will be found in detail elsewhere's on this site. Do NOT clean the slip rings, which are soft copper, with abrasives. A pink lead pencil type eraser is OK. Use of fine grade kitchen cleaning sponge/plastic light scouring pad, is OK...NOT the heavy duty type. Carbon on the slip rings does not hurt, so a bit of most any drying solvent and a rag is enough cleaning. Cleaning any excess carbon from the brushholder outsides is a GOOD idea. If you have to remove and replace a rotor, heed this warning!...USE ONLY the factory tool, or a homemade tool of HARDENED steel. Do NOT use soft steel. Information on making a tool is on the http://www.airheads.org website. The BMW factory tool is not expensive, and a good idea for one of these tools to be in your on-bike tool kit!
Brushes connect to terminals with casting stamping identification of D- and DF. D- is the grounded terminal, even though it appears insulated. Df is insulated (be sure you do not mix them up during brush replacements), and D- must go to the BROWN wire. Do NOT goof....many have!....do NOT fail to properly assemble the white plastic brush holder insulating washers at the correct Df terminal...IF you have disassembled this area. If you mix them up, you will ground the Df wire, the D- wire is grounded elsewhere's....so the GEN lamp will light up, but you get no charging!
NOTE: When brushes get worn enough, and the snail spring will touch its own side-notch in the white plastic brush holder, and even very slight and acceptable run-out (wobble) on the rotor can cause intermittent contacting of the brushes. This can vary with rpm, making you think that you have a rotor that might be opening at higher rpm.
9. If you have to remove a diode board, when replacing it, note that the black wire goes to the starter solenoid, and the blue wire goes to either of the D+ terminals (one D+ terminal is not used). Alternator STATOR housings have three terminals next to each other, the three mating wires may go to them in any order. They MUST fit tightly. A /6 and later diode board has an extra terminal on the left side, and a wire from that terminal goes to a terminal on the stator housing. Diode boards of all models can interchange, but a /5 board will give slightly lower charging in a /6 system.
10. The headlight
shell may contain a parking light lamp socket that may be
unused....such as on RS and RT models. I am NOT
talking about the separate eyebrow lamp! A 10 or 20
watt quartz lamp can be installed at this unused lamp
socket. Phillips bulb 12452 is a 10 watt quartz, has PLENTY
of light output. The stock lamp in those sockets, when
being used, was only 4 watts. The 10 watt quartz can be
used instead of the headlamp, saving some power.
11. The early spark plug caps were 1000 or 1200 ohms, not
the later 5000. It really does not USUALLY make a difference on a
stock 1980 and
earlier points bike if
you use 5000, but 1000/1200 caps MAY give slightly better
performance if other things are marginal. NGK makes
nice spark plug caps. LB05F are 5000 ohms, LB01F are 1000
ohms. Check them with a meter before purchase,
be SURE they are correct....as they make similar ones that are
10,000 ohms, DO NOT use LB10F. ....and they must NOT be
used. Do NOT use anything but 5000
ohm caps on the electronic ignition models (1981+).
If you have a POINTS model, without any electronic ignition
module, etc., and you are replacing the spark plug caps, use 1000
ohm. NEVER use the carbon type of
resistance wire. I recommend AGAINST resistor spark plugs.
12. Ignition cutout problems after some miles on the road on 1981 and later models can be due to overheating of the module under the tank. It is NORMAL service to remove the module and clean and replace the electronic heat-sink grease every couple of years.
13. The /5 bikes had a 180 watt alternator. This can be updated to a specific version of the early 280 watt alternator used in 1974 and maybe early 1975. You can identify which /6 alternator stator you are looking at, by the stator size....if the one to fit a /5, it is 105 mm; all the rest are 107 and won't fit a /5. You can use the /6 diode board which has the Y connection diodes for the stator, or just use the /5 diode board, BUT, with a modest reduction of the 280 watts. Later rotors and electronic regulators CAN be used, and require no maintenance, and fit perfectly. Bosch stators have a Bosch number on the HOUSING. The numbers ending in -001 and -002 are the early type, and are 105 mm. -003 is a R90S stator, and will result in slightly reduced output. -004 and -005 are the 107 mm stators. Rotors for the earliest bikes were 73.4 mm in diameter. For the 1975 /6, and later, the rotors are 73.0 mm in diameter.
You can get a later stator and in a kit from Motorrad Elektrik. They also have a higher power alternator conversion for the later 107 mm stator bikes.
There is an EnduraLast permanent magnet alternator conversion kit available that will fit all models of airheads...with LOTS of wattage output. Kits in 105 AND 107 mm are available.
NOTE: there is some testing
that seems to show that the latest low ohm rotors do slightly
better in all models for lower rpm charging.
14. Electronic regulators WILL substitute for the earlier
mechanical regulator, the plug is the same, and it fits in the
same mounting holes. The BOSCH metal can electronic
regulator, which looks like the Bosch mechanical metal can
regulator, but is a bit shorter, works the best.
15. Wiring up heated
grips.....and other situations, including series-parallel
switching, ETC:
Typically, for heated grips, you need a method to be able to
reduce the high heat that would occur with both grips having full
power on them. BMW uses a resistor and a hi/lo
switch. That works OK. Use of a power rheostat
is not overly practical, as its physical size would be fairly
substantial.
In order to reduce the heat from grips, there are three
'practical' methods:
a. Sometimes I am asked how
to wire up a single switch so that something, such as heated
grips, can be operated, via a single switch, for both as parallel
and as series connection. Here is how to do that. You
need ONE switch, and the switch is called "Double Pole,
Double Throw", or, commonly, DPDT. The switch has 6
terminals. You can purchase these switches
commonly in two position; or, three positions, the 3 position
type, which I usually recommend, has the center position being
OFF. In that instance it is "DPDT-Center
Off". Turn the switch upside down so you have a
vertical row of three terminals on the right, and three on the
left. The center terminal of either the left or the right
is always the moving contact for that side. On the
LEFT side, connect the center terminal to +12 volts, probably via
a fuse and possibly via your key switch. Connect the UPPER
terminal on the LEFT side to Load #1. Connect the
CENTER terminal of the RIGHT side to this SAME upper left
terminal. Connect Load #2 to the lower terminal on the LEFT
side. Connect the not yet connected Load #1 wire to
this same point. Connect Load #2 unconnected wire to
GROUND. The last connection is the LOWER one of the RIGHT
switch side, ground it.
NO connection is to the upper right side of the switch.
Here is this sort of thing in much much more
depth, a more graphical explanation:
Ground one side of one heated grip...let us just say this
is one of the Right grip wires. Connect the remaining right
grip wire to one of the left grip wires. On the switch,
connect the center (arm internally) of one section to the
+battery after the ignition switch, but via a 4 ampere
fuse. On that same section of switch, connect one terminal
to the left grip wire that had no connection. On that same
section of switch, connect the other terminal to the JUNCTION of
the two grips wires made previously. You now must wire in
the second switch section. On the same end of the switch that
connects to the ONE left grip wire, run a short jumper to the
CENTER (arm) of the other switch section. The same end of
the switch, opposite, other section, has no connection. The
remaining connection of the second section is connected to
ground. When switch is in center position, no power
goes anyplace. When switch is in one position, +12 goes to
arm of first section of switch, then to the left grip and to the
arm of the second section. +12 travels through the left grip,
through the right grip, and then to ground. Thus, this is the LOW
power, or series connection. When the switch is in the other position, the
first section of the switch applies +12 to the junction of the
two grips. One grip, the Right one, then goes to ground. The
other is grounded via the second section of the switch.
This is a sort of graphical view of the rear of a DPDT
switch, with the O meaning a terminal, and my adding of alphabet
letters next to each one. It is critical that the switch be wired
EXACTLY as described below.
Oa Ob
Oc Od
Oe Of
Connect two grip wires together. Ground one right grip wire. No
connection is made to terminal b.
Connect +12 to c, via 4 ampere fuse and to the output of the
ignition switch. Connect a and d together with a jumper wire.
Connect e to the junction of the grips wires previously
joined. Connect the a-d connection ALSO to the left grip
wire. Ground f and ground the Right grip.
NOTE that the wattage in a circuit follows Ohms Law. Because of
this, when grips normally in parallel mode are changed to
series mode, the heat (wattage) produced, assuming both grips are
identical in resistance (which they are, close enough), is reduced
to a fourth of the parallel amount. This is a low value,
but may be acceptable
if the parallel connection is WAY too hot...which is not at all
uncommon with aftermarket heated grips. The Law I
mentioned is: voltage squared, divided by resistance, equals
watts. What this means on a practical basis, is that
using the worst case (a 14 volt level whilst cruising), the power
is 196 divided by the resistance. If,,,,for just an
example.....the grips are 15 ohms EACH, in normal high heat
'parallel mode', then EACH has 13 watts of heat. If the
grips are in series, then the resistances ADDS, and you have 30
ohms. Now the heat is a TOTAL of 6.53 watts.
3-1/4th watts in each grip is kinda low, still, it is feelable....barely
though. THUS, using a series and parallel switching method is
NOT what I
recommend.
b. Heat grips are normally
wired in parallel, and a switch used to turn them on and off, and
a secondary, low power position is on the switch....and, in that switch position, a
resistor, which is actually a wire of a special type, lowers the power to the
grips, but that resistor itself can get HOT. This actually works well.....if you
like the setting of the Low position, and the wire is routed properly, or if you
use a resistor it is mounted
properly. BMW basically did it when it installed the heated
grips....or your dealer installed the BMW grip heating system.
c. This is the preferred
method for some installations: Use a small
control box of the type that is used for heated
clothing. These vary, but the ones that control via
pulsing or duty-cycle are the best, as they hardly get warm
themselves and are very efficient. Typically these have a type of
'transistor' inside, that is controlled by the adjustment
knob. At a very low heat level for the clothing/grips, the
transistor is turned on 100% for a fraction of a second, then
turned off for a much longer period of time.
As the heat control is adjusted higher, the ratio of on to off
time varies, until at full heat the clothing/grips are on all
the time. Because there is hardly any 'resistance' in
the semiconductor no matter what the adjustment is set at (provided a pulse
circuit is used), heat
developed is quite low, and efficiency very high.
Most light dimmer controls in your household work
pretty much the same way. Basically these devices, to
describe them another way, act like you are manually operating a
switch, for either a short period of time, or a long period of
time. Unless you are good at electronic design work, it is
better to purchase one of these little boxes.
The cheapest way to go is the single resistor
method (b.), which actually is quite decent...but you need to find the
right value of resistance...and mount it in a place the heat in
it is no problem. A 6 ohm resistor was used by BMW on many models.
16. Craig Vetter's Windjammer fairings have on-line help available, including the wiring diagrams, information on saddlebag and windshield mountings, etc.
17. Any stock airhead electrical system, (including the /5 180 watt system), will maintain the battery in a charged condition, from something like 2200 rpm....to certainly not over 3500 rpm....ONCE the battery is fully charged. The later model airheads have some slightly higher power usages, and almost always will require 2800 minimum. Adding an electric vest will raise the rpm required a bit....perhaps a FEW hundred rpm. Continuous riding below 2800 is not good for the engine. Any really appreciable electrical load may require 4000+ rpm, continuously. On a practical basis, considering sometimes poorly maintained electrical systems, old components, etc., don't plan on over 80% of the rated watts output of the alternator. Commuters (stop and go, heavy traffic) will have more problems keeping the battery charged.
18. Folks sometimes ask about the wiring
diagrams for such as the 4 way flasher, various versions of
headlight switches, and so on. Some of this
information is in some factory manuals, rarely in owners manuals
to any degree, and almost nothing in such as Haynes or Clymers.
Reference can be made to information on the R65 4 way flasher
(hazard flasher), which has application to other models, and on
other items mentioned here in #18....in the 1985 service fiche
#4, section 61. That will also provide information on all
the 1979 models for adding a headlight on off switch, applicable
to others, ETC. There are also other sources. I
have most of the information. There is a separate article
on this website for these things: misclelectrical.htm
19. The earliest /5 model was not
fused. The later /5 model fusing
really should be
added. Besides that, the /5 and early /6 bikes did NOT have
any short circuit protection for the headlight flasher
circuitry. I recommend a fuse be added ....or, at least, a
fuse in the main power lead from the battery (not the starter
wire though). Just adding a fuse in the battery
circuit will be of some help on any of these models, if you don't
want to add the proper fuses at the proper place in the headlight
shell. The later blade type fuses are more
reliable than the tubular types.
20. BMW has two bulletins out on certain models built from 1985 into 1989, regarding the brake light switch on the handlebar, and the switch at the rear brake lever. The information will be found on this website at brakes.htm
21. Here is the URL for the Chicago Region
BMW Club, the source for their various repair manuals.
http://www.crbmw.com/content/view/22/46/
The
Electrics manual is now priced at $30, is simply THE best
electrics manual for airheads, and Oak was primarily responsible
for that manual. HIGHLY recommended.
That website, shorten the URL, also has some information on
the background of that Club, and the background on Oak, etc., and
those various manuals. My CRITIQUE
of the electrics manual on this site: chitechelmn.htm
22. The R100R models PRIOR to serial
0280227 (the last 7 characters in the VIN number) have a problem,
and need an additional grounding wire, on silver-painted frames
models. Failure to have this added ground wire added
will show up as misfiring...or...poor alternator
output. ADD a wire between the left starter motor
cover, and the ignition module bracket.
23. The /5 bikes
use a 2 terminal flasher relay unit. It is load and voltage supply
dependent, so flashing speed varies with alternator output (rpm)
The following is an acceptable substitute:
25. If you have a 1979-1980 R65 (maybe R45 too??),
check the front ignition coil mounting bracket. They
tend to crack, and the ground wire there becomes
disconnected. You will find funny electrical
problems if that happens (like maybe a crazy tachometer,
lights doing weird things....).
26. Sometimes
there are complaints of hard-starting bikes. The owners
have checked everything, including valve adjustments, compression
pressure, spark plug wires and caps, coils, everything....and the
bike still does not start OK. Check the slides on CV
carburetors, be sure they are fully bottoming.....there is a
spring on top of the slides on some models, to help with this.
27. A RARE, but super-annoying problem, because you
likely will go CRAZY before you find the answer, is one of
the 1981+ electronic ignition airheads, that typically will
idle OK, but won't raise its rpm up properly.
This problem acts somewhat similarly to a hole in the
carburetor diaphragms. The actual problem is a
poor ignition kill switch at the bars. Cleaning
that switch may not fix the problem. Bypassing the
switch will show whether or not the problem is that switch or
not.
28.
Revisions:
06/29/2003: Total revision this entire article,
combining of electrical hints and electrical problems pages, and
moving some items to appropriate places on the website.
07/20/2003: add #20
09/05/2003: add information to #2; modify #3, #7, #13
and #19 all slightly
09/21/2003: add note 2 to item #8; move #18 information to
#8, and add new #18 information, modify #19.
01/05/2003: add #21
03/15/2004: Corrections to item #6...several actually.
04/11/2004: Expand #3 with all the red information
07/05/2004: Expand #8
10/15/2004: Redo and greatly expand #15 for maximum clarity
03/21/2005: expand on neutral switches
03/28/2005: update #3 for hyperlink for cricket fix; revise
#4 slightly
04/09/2005: add hyperlink on 21
11/27/2005: In entire article, go through and clarify
things. Add R100R information too.
11/23/2006: Clarify Monolever 1987+ diode information
inside starter relay
04/15/2007: expand #4
01/06/2008: fix chicago club's hyperlink and description
01/07/2008: fix vetter's URL and .crbmw.org url
06/28/2008: minor clarification about monolever diode problems
10/28/2008: Add #23
02/23/2009: Clarify #13
06/08/2009: Expand #23.
11/04/2009: Add #25.
11/21/2009: Move #26 information from end of #3 and make it
#26. Go over entire article for clarity.
12/05/2009: Add Signal Stat information to #23
02/11/2010: Add information to #27
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