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I have a '37 Packard 120 CD Touring Sedan with the Autolite generator and Autolite VRD 4001A voltage regulator. Amp gauge was showing a discharge when running (with no lights on) and battery kept running down. Generator tested good: was putting out 8 volts with no load and 7 volts with a load. I did the ground wire from field terminal on generator test (which I read about on this site) and amp gauge suddenly showed a charge. That pretty much isolated my problem to the voltage regulator and I plan on having it rebuilt.

Here's my question: for about a day after I did the ground wire test, the amp gauge still showed the system was charging - then suddenly it stopped. Out of curiosity, I did the ground wire test from generator field terminal again and (again) it showed a good charge. The system continued to show it was charging for about another 2 days and suddenly stopped again. Can a voltage regulator issue be intermittent and what about the ground wire test would cause the issue to (temporarily at least) clear?

I suspect your cutout relay has intermittent continuity.

With just the ignition switch on, does the amp still show discharge? If so, something, like an accessory, may be on. Or you have a short, which are notorious for being intermittent. A bare wire touching and not touching, for instance.

Humanpotatohybrid, which should be resolved with a rebuild of the voltage regulator, correct?

With the ignition switch on you may see some minor discharge as things such as the gas guage, clock, etc then have power. Also, the Coil has power at that point.

On my car which has an alternator, so not exactly the same, the Amp meter will go pretty much to 3/4 charge mark right after starting and the car on fast idle. Which is system replenishing the battery drop from the battery from starting. Over the course of a few minutes, the amp meter slowly moves back to the middle position.

If I'm sitting at a traffic light, with the motor at a low rpm, if the turn signal is on, I can see the Amp meter twitch slightly with every signal blink.

The alternator has a higher rpm exciting point then the normal engine idle. So if I turn the car off, and then repstated it after the car is already warmed up, the Amp meter will show discharge. If blip the gas pedal to bring up the rpms for a second, the alternator will kick on, and the it will show charging again, and the settle back at the mid point.

Joe,

A minor draw when ignition is turned on - maybe 5 amps. I attributed that to the gauges coming on and coil. That still would not seem to explain why the system consistently starts charging (for a while) after the field ground test.

Big Kev,

That's what I attributed the slight discharge when I turn the ignition on to - coil, gauges, etc.

Am going to have the voltage regulator rebuilt and see if that solves the issue - it's what all the diagnostics point to in any case. Just do not understand why system will work correctly (for a period of time) after grounding the field terminal on the generator.

It's not uncommon for a voltage regulator to work intermittently. A couple of things you can check before taking anything apart:

1. Be sure there is a good electrical ground between the generator frame and the base of the regulator.
2. Do the routine that gets the system working, and the next time it quits working, tap the regulator lightly with the handle of a screwdriver or something similar, with the engine running a little above idle and accessories off, and see if it starts charging again. If it does, it indicates corroded or burned contact points in the regulator. Sometimes, very carefully cleaning the contact points will restore reliable operation, but be warned that the regulator is VERY delicate and easily damaged or thrown out of adjustment.

Grounding the field terminal bypasses the regulator contact points and forces the generator to work, and the cutout relay closing may disturb the field contacts in the regulator enough to get them working again temporarily. Tapping the regulator cover will often do the same thing.

Quote:

Grounding the field coils spikes the voltage really high, though this is normally not noticed since the battery "absorbs" the spike by simply charging. (Note that this may harm the battery... this is basically how third brush systems work.)

Spiking the voltage causes the cutout relay to close much stronger than it normally would, which between the force and the inevitable slight deflection of the contacts, makes it work when it no longer would in the typical closed position.

TxGoat,

Thank you - will definitely try that tapping. Will forego trying the cleaning of contacts and just have the regulator rebuilt.