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Adding Running Lamp Function To Turn Signals
Copyright, 2013, R. Fleischer
addingrunninglamps.htm-34; O15

This article deals specifically with converting the two Airhead rear turn signals into running lamps, while retaining the original turn signal function. Much is, however, applicable to the FRONT. 

This article does not deal directly with conversions to the Classic K-bikes, such as the K1, K75, K100, K1100.  MUCH of what is in this article on the physical modifications ARE applicable to K bikes, Oilheads, ETC.   The K-bikes have a bulb-monitoring relay; which complicates matters, and information on modifying them is in item #2 in


I believe that this conversion ADDS to safety.   You get more rear facing lights, and you have two lights that are lit in case your one stock running lamp burns out.  NOTE that many bikes have only ONE rear running light...if it are INVISIBLE to cars coming up to your rear!!!!...which is an argument FOR this conversion.

My primary argument against this conversion is that the turn function is less noticeable to car drivers....due to the running lamp function in the same lamp, same housing.   You must decide for yourself.  

The conversion may not be legal in some States, not sure anymore.... if the lens is not re-colored to be RED (or the lamp colored red).    Careful selection of bulb and possibly inclusion of reflective aluminum foil may mitigate conversion visibility problems, if any. 

Explanation:  There is a potential problem with the basic method which I do to convert the rear turn signals into running lamps (I do the fronts too, another story).   If not done well, the turn signals are not overly distinctly different from the running lamp function.     If carefully done, they certainly CAN be very distinctly different.  Several ways to go about it, including a small unpainted or no red insert area, in the middle of the lens, or, a band across the center (I prefer that type).  One can find red bulbs too; plus the mentioned aluminum foil, IF NEEDED.   One must also understand that, in general, the reflectors and lenses of the stock bike are OPTIMIZED for incandescent lamps, NOT LED types.  Use of red lenses can be helpful in some circumstances.

The conversions in this article are for incandescent lamps.

NOTE!!...California, as well as other States, have very specific requirements about lighting.  The requirements are certainly not the same for all States.  You may want to find out what your State vehicle code says on the subject.  You can use such as Google, to search for the vehicle codes.    I won't get into the legalities, that may vary state to state, but this conversion is believed legal, or at least quasi-legal, if done correctly.

California V.C. 24603 says, amongst a lot of other things, that California does permit, for a vehicle manufactured before 1/1/79, to have red OR YELLOW stop lamps.   Further, a section in 24603 says that supplemental stop lamps on the sides, can FLASH, towards the direction a turn is being made.
Some States, if not most or all, will have such or other allowances/ordinances/regulations.    This can mean that you can add red color to the lens or lamp, or partially, or leave the turn signal lenses amber, etc.   Think about it!

The Federal Government also has its code sections, not difficult to find, more difficult to wade through.

The bottom line is that if done correctly, the two filaments in one bulb (in some cases two bulbs) in the same housing, CAN be made to look very distinctly different. 
I've personally never had any problem with Authorities for my conversions.

MORE, and DETAILED considerations and notes:

For the REAR turn signals, I have leave the lenses stock, that is, amber.  I have also used red lens material on some of the first 'new style' conversions I did, so that following vehicles see red, but to the side is still the yellow of the original plastic covers. If the HOT bulb does NOT touch the red plastic material, I found that almost any common red plastic material that will pass light, perhaps 1/16"  or less thick, will do well. Hobby stores often have small bits and pieces of colored plastic sheeting. As noted, I also did a lot of these conversions withOUT adding red material. A few I even painted inside the lens.  Some I masked and painted such as to leave an amber stripe horizontally, centered vertically, and about 1/4" in height.   I have also done some with a masked amber round area in the center.
You might consider using a red lacquer or other plastic compatible coating on the inside of the amber plastic lens....but only on the extreme rear, not the sides of the plastic lens (maybe not noted).  Consider also just leaving the lenses alone, and not using colored inserts, not painting, not using colored bulbs.  I had good luck with some red nail polish on the inside of the otherwise stock amber plastic cover one such conversion.

In one conversion, I left the original amber plastic lens alone....but installed a RED lamp...I found these lamps commercially available at the time.....and I then used a sharp knife to remove a fair amount of the red material from the lamp that was forward (as fitted) from the rear top of the lamp.  That gave white light to the sides, red to the rear.   It worked OK, but now there is no super easy way of replacing a lamp, and red lamps are not super common either.  They may be more common now.

NOTE #1: Much of this article's information is also applicable to the front turn signals.

NOTE #2: The turn signals on the stalks models are very similar, front and rear. The turn signals in the RS and RT fairings are different, but the sockets similar. Thus, one may use much of this article's information to convert the front turn signals.  BUT...for the front turn signals, while they CAN be converted in a similar way, I have also used a method in which I drilled the reflector and installed a very small lamp in its separate small socket, sideways. That was an experiment. I really do prefer the conversion of the socket as described below.  Obviously, for the front's, you do NOT use red material or paint.   The front socket and setup is different for the faired versus un-faired models.  But, the principle is exactly the same.  You may have to run a wire to them...on the RT, perhaps from the eyebrow light; it is very simple.

NOTE #3: I did contemplate making the rear turn signal housings 'all function'...that is, incorporating a few diodes to make them act as run and turn; but, with diodes, adding a brake light function.  I never did the engineering work, although it most likely can be easily done.

This article sounds complicated, but isn't. Please read it through a few times before doing anything.

First you should remove the outer plastic lens cover over your taillight and the cover over the turn signals, pull the innards out just a bit, and LOOK at things.    READ this procedure through, as you look at these areas. 

NOTE that the plastic lens covers should NOT have their mounting screws over-tightened.. you will break or crack the lens.  Note also, that SOME plastic lens covers can ...or should....only be installed in one direction.  A drain area is usually provided on the lower edge.  SOME can NOT be installed with the TOP marked area on top!!...that is normal!!

The #1176 is NOT an offset pins lamp, and I do NOT recommend you use that lamp or the different part numbered NON-offset socket it requires. In my very first conversion, DECADES ago, I originally used that 1176 lamp, using a mickey-mouse jumper soldered to a lamp contact.  Why?...well, I had a lamp and socket. 

On a later conversion I modified a BMW single contact socket to change it to TWO contacts. Again, NOT recommended (mickey-mouse), and because you WOULD have to identify the bulb contacts as hi and low power, each time, some soldering for every bulb change unless you hand made contacts...well, this is ALL very messy. For those that insist on knowing about the #1176 lamp: 12.8 volts, 1.34 amperes, a lower 21 mscd, and 14.0 volts, .59 amperes, 6 mscd.
On a practical basis it is not of much value to know that stuff, just use the lamps and methods I recommend in this article. 

Use of larger even more higher powered bulbs is NOT recommended.

The particular socket I have selected, and recommend, has the usual two side mounting pins, but the pins are offset in the (lengthwise) bulb fitment, so the bulb can ONLY be installed in one position, NOT 180 the other way.   This is standard for lamps which are often used for running and stop (brakes) function. It is pretty much standard for ANY two functions in ONE lamp usage.

Using the 1157 (2157) bulb with its length-wise offset pins is a FAR better choice than non-offset types like the 1176. Using a common 1157 (2157)  lamp ENSURES that, if properly wired at the socket, you will have a BRIGHT turn signal, and considerably dimmer running lamp, which is what you want....AND...bulb replacement is easy, as it can only go in one way.  NOTE that the Euro type of lamp which is quite similar enough in specifications is number 7528, it is a good lamp, but you can use 1157, 2157, or 7528. I highly recommend NOT using a NON-offset 1176 lamp.
There is a lot of semi-nerdy and nerdy information on these lamps, here:  If you really want a lot of information, the real story, please read that article.

When this conversion was originally announced on the Airheads LIST, a PS34240 numbered part was used for the socket. That is a Borg Warner product number. Pep Boys and other places sell Borg Warner. However, later, when I purchased the Borg Warner part, it was part number PT11 in their catalog. It was a nicer than the Napa part, which was Echlin brand #LS6538, but that will also work just fine.

Some LED lamp units are on the market, such as from, that offer a unit, such as a 1157 replacement, that has LED's pointing sideways and to rear.  They have a bright section and a running section.  Some reflectors will accommodate these nicely, some don't show enough of a change between run and turn.  Some flasher relays on SOME models will require changing to accommodate the low drain of the LED unit.  I don't like using resistors to increase the drain to enable problem flasher relays to work.  

Now-a-days the 1157 LED replacement is available in YELLOW as well as RED and WHITE illumination.   The yellow works fine with yellow lenses.  While you can use white, I think using the SAME LED color output as the LENS color, is best.

I still think LED's are not as good, for visibility, in this conversion, as using incandescent lamps.
My thoughts are open to modification, if I see an LED unit that is as good or better.


What you are going to do is modify the stock socket/reflector, which is one unit, to accept a metal socket with two contacts for a #1157 (2157) or 7528 lamp.  The particular socket I have selected has the usual two side mounting pins, but the pins are offset in the (lengthwise) bulb fitment, so the bulb can ONLY be installed in one position, NOT 180 the other way.   This is standard for these lamps which are often used for running and stop (brakes) function.

Those lamps can fit into the socket in only one position, due to the offset pins on the #1157 (2157) lamp (as opposed to the 1176 which I recommend requires a different socket than I specify, or modifying the BMW socket, which is very messy to do).   The Euro version of the lamp is #7528, which has a silver-colored base, and is actually preferable.

You are going to modify the stock socket/reflector, ream the existing hole or otherwise make it slightly larger but a good solid FINGER PRESS FIT for the SOCKET, sand the socket, epoxy in the new socket in the correct rotation and also for the in-out alignment, and then connect existing wires, and add one wire for each turn signal, and solder on the original BMW socket grounding tab. This is exactly how it is done for the REAR turn signal housings that are on most airheads, said housings typically are on a round metal stalk tube.

The first order of business is to look at your bike, make your decision(s), and then obtain the new lamp sockets!

Remove the BMW bulb holder (this is the reflector assembly) grounding contact in the turn signal unit; and, ream the plastic center hole for a fairly tight finger-push about 0.650 inch will be necessary to snip off the little original plastic tab that kept the original bulb from going deeper than a certain point (a few reflectors do not have that). DO measure and hand fit, YOUR NEW SOCKET, to the BMW reflector. YOUR socket may not be exactly the same as mine was. A common hand reamer works fine here on the plastic reflector, from both sides, a tad at a time.   You COULD use a round file, but please keep the hole nice and ROUND, and the less taper the better.  The socket should be a medium push fit before epoxy work (DO NOT epoxy yet). 

I modified the sockets I purchased. They had a 0.350 inch diameter, 1/4 inch long tube area at the rear of the socket, a sort of  'stepped-down' area. You can easily remove the contact/wire unit through the front of the purchased socket. I ground off that rear tube section to JUST FLUSH and then cleaned up (IMPORTANT!)  any sharp edges on the center hole where the wires pass through. ....NOTE:   There are several types of these sockets, be sure the sockets you get have the offset lenthwise pins; that is, the two opposing places the lamp pins end up at when the lamp is installed, are NOT directly across from each other; one is closer to the aft end than the other! 

SOME sockets are made such that just grinding off the rear tube area is not quite enough. 

Install the 1157, 2157 or 7528 lamp into the socket that already has the wire, insulating washer, and spring.  Pay attention to the wires as they exist the rear hole.  If any chance those wires can contact the socket metal, then ream out the rear hole and clean it up.   Do NOT ream so far that the spring will fall through.   You can ALSO add a very SHORT piece of heat-shrink tubing (too long and it is crushed upon assembly to the bike) to each wire at its socket pin, shrinking it in place...and giving added insurance that the pin can not short to the case.  Remember, this conversion may be on the motorcycle for decades....we want NO chance of short circuits!   Once you have things properly done, and cleaned up, proceed:

 Remove the wires, spring, and insulating washer that has the two wire holes in it, from the socket.   Clean up the outer surface of the socket with very fine grit sandpaper...for good epoxy adhesion. Temporarily install the lamp,  install the socket to the exact correct depth and orientation of thinner filament. Don't push too hard on the glass....remove the lamp after deciding on orientation.  Double check this work, and be SURE that you have not mixed up the left and right reflector socket when actually installed in the bike, the thin filament is on top.  Be sure the lamp does NOT touch the plastic outer cover lens...and at the same time, the wires are not crushed at the inside.  DO NOT epoxy yet!

Now.. you'll be soldering to it:  The original BMW brown (grounding) wire will continue to connect to the original grounding clip...which removed clip is now replaced, and SOLDERED to the bulb holder, after first carefully bending its long bulb contacting tab the other way (180 degrees)(don't bend the wrong part).  That tab touches the socket in that sanded area, for soldering.   BE SURE you do a really clean, well-soldered job here, and snip off any excess of that tab length.  You won't be able to solder this adequately unless the parts are very clean and finely sanded and you should use a rosin core solder and a fairly hot iron.  Done quickly, no reflector plastic in the slightest will melt.   You can NOT do this part of the job UNTIL the socket is installed the correct way for depth and round direction.  You do that by making test-tries...that is...test installing the socket, and its rear wires loose behind, and installing it with the 1157, 2157, or 7528  lamp. The idea here is to NOT let the lamp touch the inside of the outer cover lens plastic material (that means your added red plastic material if you use it) and at the same time not have the socket so deep in the reflector that its rear wires get crushed. Spend a few minutes doing this right.   If your items allow, use extra clearance behind the socket for the wires...just so long as the bulb will not come too close to the inside of the still yellow colored outer lense.  You will have to put the reflector-socket-lamp assembly into the housing, and then hold the cover onto see the distances of the lamp to the cover.   

Some reflector units have a riveted contact/spade is used.  Drill it out carefully, and modify slightly as required.

Your lamp may have a 'top' mark on it, if so, follow that as far as rotation of the lamp socket is concerned.  When the area marked top is on top, you should see the thinner filament is on top, horizontally.
Marked or not, that is how the socket should be installed, with the lamp properly inserted in the socket.

**NOTE: The right side lens fits with the LENS lettering proper (top marked)...but the same lamp assembly part is used by BMW on the left side... installed upside it fits only one way to the metal housing (BMW flips the housing over for the other side). This means that if you REALLY want to do things orient the left side bulb filament and socket at 180 degrees to the right one...ending up so that both sides are the same regarding the BULB orientation, that is, thin filament on top and horizontal. Frankly, bulb orientation is NOT all that important...and, I HAVE seen variations on this stuff:... 

BMW has made these housings and outer covers in more than one way, and they all look the same at first glance.   The inner reflector unit only goes into the housing in one direction....keep that in mind when orienting the lamp, socket, and putting the outer cover up against the housing and reflector, when checking such as bulb clearances and socket orientation.  The outer covers have been made in two basic styles, and the drain hole area is at the bottom if you have that drain area.  Perhaps you will want to do one side at a time, and not take the chance of mixing things up and finding something does not fit.  

So...inspect your particular parts carefully!

****For front or REAR.....check the fit carefully, setting the socket to the correct depth and orientation, BEFORE epoxying that socket!!! You WILL find you can get at least 1/8" clearance from the bulb to the plastic...a bit on the extra side is nice in case of bulb variations in the future.   Be SURE there is enough room at the rear for the wires to bend sideways without being crushed!

With the new socket to the correct depth and orientation for filament, you can now clean the surface with a rag and bit of solvent, maybe use a scrap of sandpaper if need be, and then epoxy the socket with JBWeld Quikset or similar quick setting epoxy, a tiny dab here and there. Do NOT get epoxy into any slots of the socket.  You can dab in the reflector area, as well as the rear area.  I dab a tiny bit in the reflector area, then turn the unit over, leaving it reflector open side down, and do the rear.   Very little epoxy is required over-all.    Do this neatly and don't get the epoxy where it is not wanted! BE SURE the depth and orientation is correct, and also correct for the particular left or right bike housing long before you apply epoxy or do soldering!   

For the REAR, you can (unless using a paint or lacquer or other coating, as described, on the REAR INSIDE portion of the plastic lens) install some thin flat red plastic material (not cellophane!) into the original yellow lens (some paints may be OK, not on sides of the lens please), and as far INTO the lens as possible, and you need to file or otherwise shape the size of this added piece, if you use it, so its edges can be glued into the lens. want the socket depth to be such that the plastic cover fits, red insert does NOT touch the bulb, yet the socket/wires do  not bottom/crush at the rear of the housing.  I mostly just paint the inside REAR and don't use plastic inserts; as I can be creative with the painting.     NOTE here that I have mentioned, much earlier in this article, various other methods I have done with the lamp and lens.  Decide which YOU want to do. You can also decide to NOT use a colored bulb, NOT use colored material, NOT paint the lens, ETC.

Connect the original BMW wire in the turn signal housing to the BRIGHTER filament, retest with power ON, to be sure you don't mix them up. Don't leave bare strands of wire here and there. BE NEAT!!  NOTE that shrink tubing may well do a better job at keeping the connections small, as opposed to using barrel type of crimp there is limited room in the housing.

You will have to add two wires from the running lamp portion of the regular center taillight (or convenient point, depending on model of bike)  to the new running lamp filaments....this goes to the LESS bright filament. Run lamp section is green/black on airheads (white-black on Airheads with the single dual filament bulbs in the stock taillight, such as a R80ST), inside that taillight. Do this neatly, running the wire through the turn signal mounting tube. Remember that your wiring should be neat, it may have to hold up to vibration for decades.  The ST, and some other models are constructed differently regarding the mounting and wiring of the, make changes here as needed.   It is a NICE touch, if you can, to use the same wire color code for the added wires.   

NOTE: If you don't know which is which wire coming from the new socket, then before installing the new sockets, insert the bulb fully and properly, hold the socket outer metal against one terminal of the battery; and, in turn, touch the socket leads, one at a time, to the other battery terminal...and mark the BRIGHTEST lead connection as "turn", mark the dim one as "run". 

Be very sure that the wires are not crushed behind the socket!  Be SURE the wires are not cut by the end hole of the socket.  THIS is extremely important!, and the socket depth before epoxying MUST be checked!   YES...I keep mentioning this point. Remember: not too deep to protect the wiring, and not too far out to keep the bulb from touching the plastic. You will have to assemble and disassemble a few times, just to get that correct...a few total minutes. ONCE you epoxy it, it is not going to be moved again!

For the more anal types:
The #1157 bulb (or #2157) as recommended is, on one filament, 12.8 volts at 2.10 ampere rated (this is 26.88 watts), 32mscd light output. That higher powered filament is for turn signal (or brake) function. The other filament is 14.0 volts at .59 ampere (8.26 watts), 3 mscd. That is the 'running' filament function. This is proper, that 12.8 volt rating, because when the brakes and/or turn signals are in operation, the higher drain pulls down the system voltage a bit, due to little voltage drops here and there; AND, the manufacturer's tend to have the bulb a bit over-voltaged anyway...although this does reduce its life. Don't worry about it all, I am just mentioning it in case you notice a chart of specifications.  The original turn signal lamp had the same situation. Some lamps have nominal "12 volt system" ratings, and have another voltage rating that is the real rating.  I get into these 1157, 2157, and 7528 lamps ...and a lot depth, here:

With the lamp having at least 1/8th inch clearance from bulb to the red lens, there have been no heat related problems on my conversions. Much over 1/8th inch is unlikely to be had with an added red plastic material unless very thin (no problem with painted lenses)...and still keep the wires from being crushed. There have been NO problems without the red lens either...I have done about twenty of these modifications; some with NO red material added. Probably not really legal.

 If you use a coating, find a red paint of some sort that will stick to the inside of the yellow plastic lens quite well, and thereby not have to install a piece of reddish plastic material. Do NOT paint the inside side walls  of the yellow plastic lens. 

Regarding the more common of the grounding clip styles removed from the BMW socket: 
I bend the forward facing portion that originally contacted the side of the original BMW bulb, rearward,
    and then reinstall the clip thing;  solder it, using a high heat soldering the cleaned and
    sandpapered new socket metal. I prefer this to the original pressure contact method...which you could
    still use, if you wanted to....and, in fact, I have found that also adequate....although you will have to do a
    bit more hand it requires a slightly flatted area.

I'm often asked about what turn signal flashers to use if the old one is no good.
This is copied from
NOTE that article has the latest information, the information below may not be the latest.

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:

   Tridon Stant

   Electronic Extended Life Flasher

   12 Volt, 2 Terminal  EL12
   Actually, almost any of the two-terminal flashers will work OK.

After the /5, the stock electronic flashers are a bit complicated inside.  There are three different uses of these flashers.  One version, used on 1978-1980, had terminal KBL on the flasher connecting to the single dash indicator lamp.   Another version has the single turn signal indicator lamp connected from the left lamps to the right lamps, and there is no usage for a KBL type flasher output.  The final version has two separate turn signal indicator lamps, such as on the R65, ST, GS type of instrument pods. The BMW flasher is rather pricey, and has special indication when a lamp burns out.  It is possible to rather easily add a piezo tone unit to any of the flasher setups. Much cheaper substitutes that are perfectly OK, are just about any car type electronic flasher, such as a Tridon, from the autoparts store.  These don't use the brown ground wire that BMW's flasher relay does. A recently recommended substitute is the Blazer (or, Tridon/Stant) flasher.  The model used was 550, which is a thermal flasher, but handles the BMW lamps just fine, and would even handle extra lamps, such as on a trailer or hack.  En electronic unit could also be used. Connect the P terminal to the indicator lamp (usually a green wire); the X terminal to the power (old terminal 49 wire, green-black); and the L terminal to the load (old terminal 49a, green-yellow).  If you have two INDICATOR lamps, don't connect to the P terminal.


05/11/2003:  add .htm title
05/14/2003:  editing for clarity
06/23-24/2004:  modify instructions for bikes using single bulb rear tailight unit; clarify in various places to
                    cover all models, and upload to Internet.
03/23/2006:  minor updates...mostly clarifications
05/06/2009:  Rechecked, and made minor clarifications again.
05/25/2009:  Add the California 24603 V.C. information, inadvertently left out a long time ago.
06/08/2012:  a bit more information regarding the Euro lamp 7528, etc. Add hyperlinks to my lamps article.
09/10/2012:  Slight updating inside article.  Add link; add QR code; change Google advertising layout.
04/27/2013:  Revise the entire article for clarity, but with only MINOR technical information changes.
10/04/2014:  Clean up some



Copyright, 2013, R. Fleischer

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