Testing Voltage Regulators
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testingvoltageregulators.htm
article #20
Note:
Information on voltage regulators is also found at http://www.airheads.org,
Technical tips section. FURTHER, there are articles on
servicing or adjusting the various models, or making them adjustable on this Snowbum website and the above
website. Almost any voltage regulator found
in a junkyard car that your plug fits into, will work. There are sources
for adjustable and non-adjustable ones. Just one of these is the
Borg-Warner (Pep Boys, etc.) R588, and far cheaper, probably, is the Transpo
IB301A which is adjustable. Here are two URL's for Transpo: http://www.transpo-usa.com/usamap.htm
http://www.transpo.de/cgi-win/product.exe?IB301A
NOTE: BMW offers a higher output voltage regulator that many have installed. It is standard on the Authorities (police) bikes, it may cause you to check the water level more often if you do considerable highway miles (flooded type batteries). The regulator ends in part number -737. It is rated for 14.5 volts at 20°C; 14.3 volts at 30°C.
TESTING:
Method #1: UNplug the voltage regulator. In the socket, not the regulator, jumper the opposing two female's, they are likely blue and blue with black stripe.
This is a good time to obtain two of the standard male spades, a 4 inch or so piece of wire, and make a jumper wire to keep in your on-bike tool kit. The reason is, that if the regulator fails, you CAN get home with the socket jumpered, if you keep the rpm down so the battery does not overly 'cook'.
With the socket jumpered as described, and monitoring the battery, or at least the bike's voltmeter (if it has one), start the engine and slowly raise the RPM. The GEN lamp should go out, and the voltage begin to rise very fast, especially if the battery is near fully charged. Don't leave the engine at high rpm very long, as the voltage will rise to over 15 volts, cooking the battery. This test BYPASSES the regulator, telling the alternator, in effect, to put out whatever maximum it can. If the alternator produces lots of current and voltage, and does NOT come up to at least 13.6 at the battery, or so, with the regulator replaced, the regulator is faulty. NOTE that the fairing voltmeter may read about .3 volt lower that a battery reading voltmeter would.
Method #2:
The following is a generic method, definitely not for everyone, as you need an adjustable power supply. A regulated power source of high
stability is NOT needed. However, the voltage should be a fairly 'clean' DC...that is, not too much A.C. riding on the D.C. Most 'bench'
power sources with any sort of built-in (or you adding) capacitor filter will do. The power source must supply enough current to
operate the lamp you select (read further...).
You can do this with ANY of the voltage regulators on the airheads, Bosch mechanical, electronic, or
Wehrle electronic, or any
aftermarket regulator out of a car, etc.
***NOTE: The electronic regulators were used with a different rotor, an early
one and a later one actually, similar, but slightly different resistances, and
both later types used with electronic regulators have a low resistance, and the electronic regulator is
capable of passing the increased current demand of that later rotors, and will have no
problem with the earlier /5 and /6 type higher resistance rotors. Thus the electronic regulators can be used on all years of airheads
including the /5/6/7 and later. The mechanical regulator MIGHT NOT last too long if used with a 1981 and later rotor, I have no proof of this, it
is purely conjecture on my part. Use of the mechanical regulator in a 1981 and later airhead should be considered an emergency measure,
as the vibrating/arcing contacts MIGHT upset the electronic ignition.
The regulators all have THREE male spade connections. One is marked D+, one is marked Df, and one is marked D-.
Connect the variable power source positive (+) output to D+; and the
negative (-) output to D-. Connect an accurate digital voltmeter to the same
terminals. It is best to connect that voltmeter at the regulator
terminals, not at the power source terminals.
Connect a load between Df and D-. I recommend a 12 volt (nominal) LAMP...such as an old car headlight with one section still
working, or a taillight bulb in a convenient socket, or whatever you have. Don't use
a load that draws over about 5 amperes at 14 volts, 70 watts. Because you are going to be 'looking' for a triggering point, and test circuit
readings will likely change at that triggering point, I recommend a LAMP [and NOT a resistor and another voltmeter, etc.].
Turn on the power source, and slowly increase the voltage, noting that
the lamp will begin to glow. As the voltage is SLOWLY increased, the lamp will get brighter, and if you keep one eye on the digital
voltmeter, and the other eye on the lamp (hee hee hee), when the voltage reaches the 'regulating' set level,
the lamp will suddenly turn off completely. NOTE the voltage JUST BARELY before the voltage
is raised at the light extinguished point. Back off the voltage a bit and
retry several times. You want to actually know the voltage at which
the lamp turns off, but your power supply MIGHT JUMP UPWARDS when the lamp turns off...so you will have to estimate it.
You should be able to get within 0.2 volts of correct value, or even less.
Revisions:
02/03/2003: add top of page information on adjustable and other regulators
04/22/2003: add .htm title
05/30/2004: add article number to correspond with T. Index; add
voltage/temperature information on -737 high output regulator