1930 Plymouth Voltage Limiter Help

Hello,

I have a 1930 Plymouth 30U Roadster and my voltage limiter just fried and I was wondering if anyone has an idea on what may have caused this. I've been having many electircal problems recently, starting with a blown fuse and a dead battery. The battery was old and would not take a charge, so I replaced it, along with the fuse (6 volt battery and system). I also made a slight adjustment to the generator's third brush ( I moved it down a very slight amount) to try to correct a slight discharge condition when the headlights were on. This improved it very slightly and it seemed good enough. I drove it for another couple weeks (weekend driving), then I noticed that I had another discharge condition and when I would rev the engine, the gauge would go deep into the discharge range. This is when I checked the voltage limiter and saw it was not getting any power from the generator. I looked inside the limiter and it was burned out and a little melted. I assume my adjustment of the third brush must have caused this? Any other ideas on why this would have happened? I'm not very skilled with electrical problems and learning a little by trial and error, I guess the hard way.

In addition, does anyone know where I can get a new voltage limiter for this car? A cursory look did not reveal any available, but maybe I'm not looking in the right place. Thanks for any guidance on getting my Plymouth back on the road.

Has the wiring been replaced with new?

As far as I know, wiring is original, except the ignition was replaced before I bought it with a modern coil along with about 4 new wires. This replaced the original coil/ignition combo.

You may want to talk to Rhode Island Wiring Service to get a new harness. I tried to "fix" my own wiring in my '31 DB, but I am not electrically minded and nothing beats a new harness for stopping electrical problems.

Yes, it may be time for that since I keep having these electrical gremlins and the wiring is either original, or at a minimum, about 35 years old.

Answered your question on where to get a cut-out on the Plymouth Owners Club forum. I agree with others on this thread that if you have original wiring you should replace it. Rhode Island was mentioned but I've also had good experiences with Harnesses Unlimited and with YnZ's so you have several companies to choose from.

Thanks again! Your help is greatly appreciated!

Too much jumping to conclusions here.

Blown fuse = overload. Check the fused circuit for problems, such as shorting to a circuit with greater current capacity.

Dead battery = current leak or old battery. Was the electrolyte level ok? I always disconnect the battery at the starter when in the garage and connect a maintenance charger.

So, where is the short or overload? Is the replacement coil and ignition etc. wired up correctly? Might you have shorted something in the ignition switch or somewhere when this was changed over?

Is the generator OK since the cut-out melted? is it possible you shorted or changed something else with the third brush adjustment?

It is possible a new harness is called for, but a little sleuthing could fix the problem for little cost. Think about when the problems started and whether you had done something just before that.

Too much jumping to conclusions here.

Blown fuse = overload. Check the fused circuit for problems, such as shorting to a circuit with greater current capacity.

Dead battery = current leak or old battery. Was the electrolyte level ok? I always disconnect the battery at the starter when in the garage and connect a maintenance charger.

So, where is the short or overload? Is the replacement coil and ignition etc. wired up correctly? Might you have shorted something in the ignition switch or somewhere when this was changed over?

Is the generator OK since the cut-out melted? is it possible you shorted or changed something else with the third brush adjustment?

It is possible a new harness is called for, but a little sleuthing could fix the problem for little cost. Think about when the problems started and whether you had done something just before that.

Yep....with a little work, you could hunt down the problem first....like I did. Still had two "under the dash" fires. Got a new harness.

Yep....with a little work, you could hunt down the problem first....like I did. Still had two "under the dash" fires. Got a new harness.

Yep. I had that happen in my '33 back when it was only 40 years old. Focuses your attention on getting the wires replaced in short order.

As I understand it, the wire of that era used natural rubber insulation which does not hold up well to ozone (found near ignition systems), petroleum fumes (anywhere under the hood of the car), heat and age. To protect the rubber against abrasion they used cotton woven over the rubber which also does not age well with respect to maintaining strength and abrasion resistance. Finally, protect the cotton they used lacquer, also now well aged. Basically you are looking at wire that has no insulation or insulation that will fall off at the least disturbance. Basically shorts and fires waiting to happen.

Unless you know the car has been rewired sometime in the last 20 to 40 years, after the advent of plastic insulated wire, then you ought to just replace all the wiring. I guess the exception could be if you just have the car as a static display and don't ever plan on actually connecting a battery to it or driving it.

The cut outs are simple enough, but sometimes stick or fry. A lot of people in the vintage chevrolet club are replacing the old cut outs with one large diode, and sometimes two smaller diodes. With the cover on you are the only person who will know. I have one on my chev. Much more reliable. There is also a company who will take your original cut out and fit a complete voltage REGULATOR in it set to charge a maximum of 10 amps.

The cut outs are simple enough, but sometimes stick or fry. A lot of people in the vintage chevrolet club are replacing the old cut outs with one large diode, and sometimes two smaller diodes. With the cover on you are the only person who will know. I have one on my chev. Much more reliable. There is also a company who will take your original cut out and fit a complete voltage REGULATOR in it set to charge a maximum of 10 amps.

Not sure about Auto-Lite or other manufacturers, but for Delco-Remy generators of that era as used on many cars including Chrysler products there is a fellow in Oregon who makes a replacement brush band with an electronic voltage regulator on the inside. You disconnect your third brush from the field and connect it to the regulator. There is a jumper on it you can cut if you've replaced your cut-out relay with a diode to compensate for the voltage drop across the diode. The outside of the replacement band cover looks identical to the stock one so you can't tell the regulator is there. For what it is worth, I replaced the inside of my cut-out with a diode back in 1978. Both mods have been working fine for a lot of years now (the voltage regulator since about 2000).

Here is my write up on the setup: http://www.ply33.com/Repair/voltreg

But if the wiring is falling apart because it is original, you will still have issues with the electrical system.

Just adding my 2 cents worth,

I have had no end of trouble with our 1929 Plymouth and its electrics recently. i spent the last few months rewiring the lighting system because of it blowing fuses as soon as i put them. the insulation on the 80 year old wire had broken down and was touching the chassis causing a very hard to find short. the voltage regulator works on a system of an electromagnet and i wouldn't be surprised if the lacquer(or enamel, dont know what is used on that wire) insulation on the coil of wire has broken down causing the component to fail.