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Dads33Desoto

Electrical Problem with '33 Desoto

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Hoping there's an electrical expert out there that can help us sort out our problem. The generator (positive ground) for our '33 Desoto was burnt out, so we sent it out to be rebuilt. Got it back and the amp meter was showing it was discharging. So we took the voltage regulator and newly rebuilt generator to an auto electrical shop, where they bench tested it and we had to buy a new voltage regulator, 6 volt, positive ground. Hooked both up to the car and it's still discharging. Any suggestions from those in the know? My Pop lives on the San Francisco Peninsula, but I haven't found a shop that works with these oldies. Anyone know how to adapt a newer 6 volt generator with voltage regulator and make it fit on the car (short generator).

Thanks! Margaret

Edited by Dads33Desoto (see edit history)

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Hard to diagnose at a distance... I wonder if the battery is installed backwards. Or there might be a short in the system.

A little surprised you have a voltage regulator on it, that wasn't introduced until '34 on Plymouth and then only on the DeLuxe (PE) model. But the DeSoto was a big step up from Plymouth so maybe they introduced that earlier on them.

Where abouts on the peninsula are you located, maybe someone on this forum would be near enough to you to wander on over with a volt-ohm meter and help diagnose.

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Hi Margaret, the '33 Desoto is a fine looking car. What body style is it?

Since you just had the generator rebuilt and tested, it likely works fine. One thing that comes to mind - if the two wires on the amp gauge are reversed, the gauge will indicate discharge even when it is in fact charging. Check to see if amp gauge needle moves towards discharge while reving the engine, if so, you have some wires reversed. If it stays steady discharged while increasing RPM, there is another problem.

Did anyone try to polarize the generator?

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It the generator was tested then the residual magnetic field was undoubtedly set which means that polarisation should not be needed. Unless the generator and battery grounds are mismatched. A simple test with a volt-ohm meter could tell that.

Diagnosing at a distance with someone who is not comfortable with or not knowledgeable about electrical systems is not very productive. If nothing else they probably can't provide the type of data needed to do more than expensive scatter shot trial and error methods.

I strongly suspect that I am within 50 miles of the original poster.... If not I then someone else I know is probably close enough to the original poster to help out. Or lacking a local to help, their location, even just a city on the peninsula, could help to point them to a competent garage that will work on that vintage vehicle.

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Diagnosing at a distance with someone who is not comfortable with or not knowledgeable about electrical systems is not very productive. If nothing else they probably can't provide the type of data needed to do more than expensive scatter shot trial and error methods.

I agree 100%. Helping people with electrical problems can be very challenging. I'd be happy to try and help, but it is a little easier to do so over the phone. If nobody in your area comes through, feel free to contact me directly tomorrow.

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Thank you to all who responded to my posting about the generator/voltage regulator problems on the '33 Desoto. I sent all of your replies to my Dad, who btw, lives in San Mateo County. He stated he already tried what was suggested, and at this point, is considering putting a later model generator/voltage regulator on the car and somehow adapting it to fit. We (I) have his 1940 Canadian Dodge (equivelent to a '40 Plymouth) and we have a spare generator for that. If we don't get anywhere, he definitely WILL call those who offered to help via telephone. He is 83 years old and has years and years of experience with these vintage autos, but has never come across this problem before. I thank all of you for your input and suggestions.

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I'm probably not much better at helping diagnose things over the phone than by email. But my weekend plans for the mountains have been canceled so I'm looking for some place to drive my '33 Plymouth. :)

I'll likely be as far north as Palo Alto on Sunday and the county line is between Palo Alto and Menlo Park. Not a real big deal to toss the electrical tool kit into the back of the car before I set out...

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