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Charging System Test For Older Evo models and TC Models

J

Jack Klarich

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Step 1. First things first, load test the battery. Most auto parts stores or cycle shops will do it for free. Even if it measures over 12.5 vdc it can still be bad under a load. Battery is typically rated at 19 amp hours and 270 Cold Cranking Amps (CCA).

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.

Hope that helps you.
 
Ive have a poblem with my 98' ultra, the voltage guage started fluctuating, showing it was charging sometimes and sometimes not. Nowit seems as if it is running just off battery? could this be a battery problem?? regulator??? or is it the stator????

in the process of doing the steps today. Thanks!
 
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i have a 81 shovelhead i have been having charging problems for awhile. when it all started my battery was overcharging .i was getting 15 plus volts.
so i changed regulator. an i got less then 12 volts . i have since then put a new stator an new regulator , now i get 12.05 volts an less then 12 when iturn my head lights on. any help would be appreciated
 
81Shovelhead, have you had the battery checked? The overcharge could have killed it. That could be why you're charging system is having issues, it's trying to charge a toasted battery.
 
81Shovelhead, have you had the battery checked? The overcharge could have killed it. That could be why you're charging system is having issues, it's trying to charge a toasted battery.

Good point here, and trying to charge a bad battery is hard on these charging systems, load test the battery, check the standing volts, if fully charged should be at 12.7 volts
 
i also replaced battery an i am still having tha same problem i have spent the intire day checking 4 shorts. this is really pissing me off not your answers the bike lol any help would be great
 
Test your stator and regulator again. Is the wiring stock? Any aftermarket electric items on the bike? Also, what model is it? FX, FLH?

Also, if the new battery is low on charge it will drag the system down.

What is the voltage when you are rev'ing to about 2000 rpm?
 
the bike is fxr i will try the retest you suggested. battery is fully charged at 12.7 wiring is stock but has been cut on a bit that why i was looking 4 shorts.an im not having much luck with my wiring diagram.it says it is for a 1980 flt its the only 1 in my repair manual that close to the wiring on that bike.wish i could find the exact diagram

sorry at 2000 rpm its about 12.15 with headlight off an about 12.09 to 12.05 with headlight on
 
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thanks for all your help jack.it all has been helpful.i just redid your charging system test an on step 4 i found continuity between each pin an pin to fram.this really (EDIT) .the hole charging system is brannew i have spent so much time an money on this bike.an you cant return electrical parts.i guess im gona give up on this one i cant just keep spending money on the same parts.an end up with the same results.thnx for your help again scott
 
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