voltage regulator- '37 P4

[FourDoor]

Because manufacturers were experiencing poor grounds with age between the engine block and the rest of the car,and they had taken to mounting the 'voltage regulator' on the firewall or fender to get away from the generator and engine heat, they put in an extra ground wire to drag over to the regulator and generator from a 'hard' ground on the car proper. A few tenths of a volt drop caused by a poor path through the drivetrain mounting can cause the regulator to be out of factory calibration and also a problem called 'hunting'. Hence the 'remote ground'.
So you should take that 4th 'ground' wire,which I suspect it is, and put it under a regulator mounting screw with losts of cleaning to the generator body and the mounting foot of the regulator. You could also check the other end of it to make sure it is going to a good solid ground. A good idea ,and one I've done to my old chariots, is to put a steel flex grounding strap from the transmission to the chassis and one from the chassis to the body. This will insure what's called 'ground bonding' and can actually give you brighter lights,faster turnover during starts and less head scratching electrical problems especially with these old vehicles with their rusted and high resistance connections. This loss of good ground bonding is actually why many owners want to change their 6 volt systems to 12. The 12 volts makes up for all the poor connections on the high side and poor ground bonding on the low side.
You would be surprised how many of our electrical problems are not the all those small wires going around the car but the devices trying to find 'ground' i.e. the other side of the battery.?The old mechanics talk about 'getting a good ground' all the time especially with voltage regulators,generators and batteries. But I digress. Good luck.? ? ? ? ?

[TodFitch]

You have the service manual. Which is all I have for 1937 too, so I can't add much. According to the book all 1937 P4 had a third brush generator with external voltage regulation: Two coils in the box one for cut out and one for voltage regulation while the generator third brush was used for current regulation. And my book shows VRR-4003-A as the correct regulator too.

My book shows the generator should be GCJ-4802. Is that what you have in your car?

The wiring diagram in the manual shows four terminals on the voltage regulator labeled F, A, G, and B. The F connection goes to the field connection on the generator, the A goes to the armature connection on the generator, the G connection goes to a case ground connection on the generator and the B connection goes to the ammeter.

So it looks like four wires would be correct but with good grounds you probably only need three (you could put the ground wire on to one of the mounting screws for the regulator). Are you sure your NOS regulator is a VRR-4003-A? Maybe the box was swapped at one point?

By the way, have you tried dressing the contacts in your old unit? It might be tough to adjust it without a proper work bench setup but it looks like it might be possible to adjust it after you clean up the points.

[36 Ply]

I'm pretty sure that the '36 (P-2) used a cutout on the generator, not a voltage regulator.

My '36 P-2 touring sedan had a cutout; my present '36 convertible has a generator and voltage regulator from a '42 Plymouth (it was that way when I bought it).

Regards,

Pat O'Connor

[Pandanom]

I will recheck mine, '37 P-4, but I believe three wires is correct. The 4th wire may be an add on to get power to some device such as an electric fuel pump or cell phone charger. Do all the wires look factory or could one be an add on?

Jim in SC

[Chris in Jax]

Regulator on our P4 has been troublesome lately.? When I start the car it rattles/chatters until I separate the contacts above the upper windings, whereupon it makes no further noise and begins to show charging on the ammeter.? ?I have a NOS regulator that I was planning to install, but now I see that there are 4 wires connected to 4 terminals on the old regulator but only 3 termials on the NOS unit.? NOS unit is model # VRR-4003-A, correct for P4 according to the service manual.? Old unit does not have the original cover so cannot confirm model #.? Car was assembled 1/21/37 in Detroit. Could this be a '36 regulator & wiring harness?
Old regulator & NOS only have 2 sets of windings & contacts, while the service manual shows 3 in both illustrations.? All advice and counsel welcomed.......