Originally Posted by Streetrunner

I recently had the same problem but when I looked at my voltmeter the system wasn't charging, it was down to 10 volts, lucky I made it home. I recharged the battery and did a stator test with my digital VM with the engine cold and it checked OK but I noticed I didn't have battery going to my Regulator. I began to trace the circuit and it came good by itself. That worried me. The next day I tested the stator again, this time with the engine hot and it failed so I had it replaced but I still had a problem when I applied my brake i would notice the voltage drop to about 12 1/2 volts then come back up to 14 when the brake was released. At this point I replaced the Regulator, still the same problem.
When the bike was fairly new I had HD spotlights installed. Here's what I realized; when the spotlights are on and I apply the brakes and/or the turn signal the voltage would drop. If the spotlights are off there is no problem at all. I don't know if the spots are grounded or have a weak ground or if the draw is too much for the system?

Dawg, any ideas?

Originally Posted by dawg

I just posted this a couple of other places, might help you narrow it down:

Not my words, taken from somebody else, but this might help....

Step 1. First load test the battery.

Start the engine and measure DC Volts across the battery terminals, the regulator should be putting out 14.3 - 14.7 vdc at 3600 rpm and 75 degrees F.


Step 2. To check the regulator unplug it from the stator. Take a test light and clip it to the negative terminal of the battery and then touch first one pin and then the other on the plug that goes to the regulator. If you get even the slightest amount of light from the test light the regulator is toast.

To do this with a meter which is more accurate: black lead to battery ground, red lead to each pin on the plug, start with the voltage scale higher than 12vdc and move voltage scale down in steps for each pin. Any voltage is a bad regulator.
You may get battery voltage on all three pins on the newer 3 phase regulators.
The no voltage is for older type regulators with diode indicating the diode is bad and the regulator needs replacing.


Step 3. On the other part of the disconnected regulator plug. Set the multimeter for Ohms x1 scale and measure for resistance across the pins of the stator. You should read something around 0.1 to 0.2 ohms for the TC88 32 amp system.


Step 4. Then check for continuity between each pin on the plug and frame/engine ground. The meter needle should not move (infinite resistance)(digitals will show infinite resistance) if the meter needle does move (indicating continuity)(digitals will show some resistance), recheck very carefully. If the meter still shows continuity to ground the stator is shorted (bad).


Step 5. Set the meter to read A/C volts higher than 30 volts (the scale setting for voltage should always be higher than the highest voltage you expect or you may fry the meter). Start the bike, and measure from one pin to the other on the plug (DO NOT cross the multimeter probes! - touch them to each other). You should read roughly 16-20 vac per 1,000 rpm.


Step 6. If the battery was good under load test, if the stator is NOT shorted to ground, and the stator is putting out A/C voltage, then the regulator is bad (most likely even if if passed step 2).


Generally the following is true:
Check your owners/service manual for the system amp output for your bike.
22 amp system produces about 19-26 vac per 1,000 rpm, stator resistance is about 0.2 to 0.4 ohms.
32 amp system produces about 16-20 vac per 1,000 rpm, stator resistance is about 0.1 to 0.2 ohms.
45 amp system produces about 19-26 vac per 1,000 rpm, stator resistance is about 0.1 to 0.2 ohms.