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'49 3600 261 SM420 12V Generator system

Recently replaced my points, condenser, coil and voltage regulator while chasing down some electrical gremlins hiding in old wiring. Excellent coaching from Bartamos made it an organized and straight forward process (prior thread here: https://www.stovebolt.com/ubbthread...d-ign-circuit-and-grounding-problem.html)

The truck still retains its 12V generator system and it charges just fine at idle. Running down the road though I noticed a faint electrical heat smell. Not all the way to 'smoke test' level, but enough that you want to go hunting for it. Popped the hood and sure enough the new voltage regulator was too hot to hold your hand on. Not too hot to touch, but too hot to stay touching. No buzzing noises (relays cutting in and out) or any other noticeable problems.

At idle it's cool all day long, and is charging. At road speeds it's heating up (ammeter does not show charge in excess of what it shows at idle). Is this a symptom of something? Or just the new part cooking its paint?

The new VR came from NAPA and is a generic Made-in-USA replacement for mid-50's Chevy's. It has no informative markings on it. Pic of the old VR and new VR attached.

It's entirely possible that the current regulator points are out of adjustment, which causes the generator to overcharge the battery and make things heat up. Drop me a PM, and I'll be glad to walk you through the procedures needed to check and adjust the regulator for the proper voltage and current settings.
Jerry

Did a quick run to the dump, 10 minutes each way, only thing I noticed was the charging stayed high the whole trip, whereas it would normally settle to almost nothing a few minutes after starting . Got home and shut down, popped the hood and checked the VR temp: pretty warm, but not sizzling and no smoke, but suddenly noticed the generator smoking! Grabbed my 1/2 wrench, threw the carpet back and disconnected the battery, which sure enough arced big time as I pulled the negative cable off.

Looks like this brand new VR is fused. Just a bad part or is there something in the system that likes to eat Voltage Regulators?

Hmmm.... I wonder if this is what happens when you put a 6 volt regulator into a 12 volt system. Strange that there are no markings on the regulator.

Might be labeled on backside of regulator. I'm noticing a ground wire attached to regulator base on the old part but absent from new unit. Would the lack of ground cause problems? Just a thought. John

This might help:

VRs shouldn't get hot or even warm. I would guess that your generator is probably done. Without an inspection I would not rely on it. It sounds like the VR is defective too.

Thanks Gord, very helpful bulletin. Johnny N: the ground was for the electronic tach, I happened to have it off in the 'old VR' photo as I was chasing down the original gremlin (thought the new tach might be grounding the ignition circuit, it wasn't). I put the tach ground wire back in the 'new VR' photo.

This VR is a three relay version. According to Gord's bulletin, a grounded field wire would produce the symptoms I'm seeing.

The cutout points in the regulator are sticking together. That feeds the bat. current back to the gen. Your gen is probably toast now. The regulator must be grounded.
George

Hi George, the VR is definitely grounded and has all it's copper grommets.

I was checking for grounds in the Field circuit (HRLincoln's idea) and couldn't find any with the engine off. I reconnected the battery and there were no sparks flying (like when I disconnected it to stop melting the generator). So, being the daredevil I am I thought I'd fire her up and see what happens. Engine started fine and lo and behold the generator was charging! A very, very strong output for idle. Shut her down and disconnected the battery: no sparks, no discharge.

So there's no major ground in the Field circuit wiring, it has to be cutout points intermittently sticking, as George said.

Bent and crooked points in the cut out relay is the answer.

Put a voltmeter on the battery or the bat term on the regulator. It should not go over 14.5 volts with the engine reved up a little. 14 volts is ideal.
George

Thanks for all the help guys. I’m pretty organized on the mechanical side, but diagnosing the electrical system is pretty much a random walk for me, so all the experienced advice helps.

Below is a pic of the culprit: poorly made cutout relay points in the brand new voltage regulator.

I put the old VR back on the truck and the charging system runs perfectly now. Amazing that the old generator could take so much current flowing into it from the battery that it started smoking, and yet it still charges. Old school rules! :-P

There are two types of GM regulators- - - -"Delco-Remy" and "wrong"! Ebay is the best source I've found for affordable OEM regulators.
Jerry