Diagnosing Charging Problem

jagnweiner

jagnweiner

Senior Member
After 9 months of ownership, my '47 Merc has quit charging the battery. As near as I can tell, this came on rather suddenly, rather than gradual worsening, but I could be wrong. Here's what I've done so far to diagnose:

Battery is a 6V Optima that I purchased last fall (been very pleased with that). After I charge it overnight with a trickle charger, I can start the car and voltmeter shows 6.4V across the terminals while the engine is running. (not charging) The meter in the dash shows no charging (its seems to be working and previously showed charging). I started randomly measuring at terminals on the voltage regulator. Not sure which ones I'm supposed to be checking, but at least one of the combinations of terminals shows 7.2V. Others show 2-3V. Haven't done any testing at the generator yet.

So my questions are, which terminals should I be measuring at the voltage regulator and the generator? Anything else I should be checking? Thanks in advance for helping this non-electrical guy.
 
The voltage output is the B terminal of the regulator.
It is the one that connects to the battery side of the circuit breaker panel. It should be 7+ volts with increased rpm.
 
Yes as JSeery has stated above. You can connect your test voltmeter to both the "B" battery terminal or the "A" armature (generator) terminal on the voltage regulator. Readings should be 7.2 to 7.5 volts with some revs up (2000 rpm). Run it at that for 3 or 4 minutes and watch voltage which will come up a little after some running. Don't connect your meter to the centre "FIELD" terminal on the regulator. If you have these readings then your generator and regulator are good to go. Maybe your dash gauge is faulty. Regards, Kevin.
 
Armature terminal use the negative black wire of your meter if you have positive ground connect positive to the ground side connection on your regulator. The B terminal runs to the battery it shows voltage all the time but should be around 6v when not running and above 7 + when running. I like to measure the armature when running then see if the regulator is working properly then check the b side for the voltage increase.
 
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