Generator Regulator Troubleshooting


Hollis Wooldridge asked the CJ3B Bulletin Board viewersfor some advice: "I drive my 6V stock '54 frequently but it hasstranded me a couple of times with a low battery, which appears tobe from the voltage regulator (it charges, but insufficiently tokeep the battery up). Even though I drive it several timesweekly, I can put in a fully charged battery and it will bedischarged in one to two months. A local alternator shop willbuild an 8V alternator, which I'm told will help the battery, plusthe lights will burn a bit brighter. In addition, I'd have noexternal regulator or problems charging at low RPM. I'd like tohear any opinions on this setup or should I try to keep fightingwith the original style of regulator?"

Rus Curtis said: "When I first acquired my '54 3B, Ihad many charging problems with it. All told, I went through 6batteries, 13 voltage regulators and 3 generators. I wasfrustrated and felt defeated since skilled mechanics couldn't seemto fix the problem. As a last resort I took it to a reputablealternator/starter shop. Initially, I took the generator in and asked if theycould find a problem. None was found. They recommended I dropthe vehicle off so they could check the whole system and theyadjusted the contacts in the voltage regulator so that thecorrect limits were set allowing the generator to do its job. Ihad no further problems.

"The generator is actually responsible for charging thebattery. The regulator is the gate, or switch, that breaks thecharge circuit when the battery is fully charged and only allows asmall amount through to keep the battery topped-off. If it's notset correctly, your battery will drain, even if the generator isputting out plenty of charge. Keep in mind that you can get thesame results if the generator isn't up to specs either! If youhave the equipment, you can check both the output of the generatorand the voltage rating of the regulator (not just a voltmeteracross the battery terminals). My suggestion for the easiestcourse of action is let a reputable shop do it that specializes inthis. The total cost should be a fraction of what it would cost tobuild your alternator."

Ernie suggested: "If the generator is good, adjust theregulator to raise the voltage. I have had 6v systems with voltageabove 8.3v and enough to keep an 8v battery going."

Hollis mentioned: "Someone told me today thatif the starter is dragging a bit that it can drain the battery andthe generator won't be able to compensate."

1953 Auto Repair Manual

Right fenderThe 1953 Motor's Auto Repair Manual   says, "A generator regulator is designed for one purpose only and that isto regulate or control the charging rate in the generator-batterycircuit. When a good battery is low, the regulator will automaticallyincrease the charging rate until the battery becomes fully charged."

Underneath the cover of the little metal box mounted on the right fender under your CJ-3B's hood, are three units: a cut-out relay (otherwise known as a circuit breaker), a voltage regulator unit, and acurrent regulator unit.

Manual title page

Eric Lawson ran across the "Generator Regulators" section in this 1953 manual, which includes descriptions andtroubleshooting information for Autolite and Delco generator charging systems (the types used in all Jeeps).

Eric says, "It's a very good description of diagnosing chargingsystem problems. The only thing I can think to add is for the battery fully charged, generator output still high case. This condition causes lights to often burn out, maintenance free batteries to be 'wet' on their tops and 'regular' batteries to need water added more often than normal. If disconnecting the field wire at the regulator doesn't reduce the generator's charging output, try disconnecting this wire at the generator. If the charging output then drops off, this wire is shorted somewhere between the generator and regulator. If the output is still high, the generator is at fault."


Look at the full text and illustrations:


Thanks to Eric for the scans. -- Derek Redmond

See also Replacing a Generator with an Alternator, and other Tech Tips on CJ3B.info.

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Last updated 1 December 2007 by Derek Redmond redmon@post.queensu.ca