Thread: 40 plymouth electrical

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hey guys i want to redo the wireing on my 1940 plymouth just because its pretty torn up from just being old, also the owner before me started replacing all the wires but i dont like how he was doing it and there are only a handfull of wires in the whole car so its not that bad to just switch them out. Its still a 6 volt positive ground system, but at some point i want to change it to a 12 volt neg ground. We wanna get it running as is while we collect some parts but i was wondering if i rewire it now do i need to do it again to switch it to 12 volt or will i just need to replace everything the wires connect, light, gauges, etc.. Also if i want to one have to rewire it once should i use a slighter thicker gauge or should i just stick with whats there. Thanks guys.

You may want to contact Painless or Keep It Clean
Painless Performance: The Official Home Page For The Best In Automotive and Diesel Performance Products
Automotive Wiring, Lighting, & Electrical Accessories || Keep It Clean Wiring

Both of these companies specialize in replacement wiring harnesses and all of the associated components. It's a lot more difficult to "re-wire" than it would seem on the surface (it's just a bunch of wires - right?)..

Welcome to CHR
Glenn

Answers to your questions: Depends upon what your eventual configuration will be.....if you are keeping it stock and only changing to 12 v neg ground, the wiring can continue to be pretty simple. IF you are adding a different engine, air conditioning, a radio, etc, then you have a conflicting wiring diagrams....in that case, I would do a temporary wiring job that essentially matches the existing wiring. Then, when the new build arises, the temprorary wiring would get removed (or partially removed) and the new wiring layout installed. Wire is cheap. I tend to wire a car using a minimum of 16 ga for signal lines and 14 ga or heavier for power. Grounding is very important, those ground wires are essential to the circuit.

mike in tucson

I agree totally with robot why change everything twice. In the past I have bought ONE rewire kit and didn't care for it at all. I always rewire mine myself it realy is not that hard to do...If you tend to get lost just do one circuit at a time.

yea i have the diagram that matches to car, so i was just going to basically do one wire at a time. Sounds kinda like a pain but that way i can make sure its done right and nothing is missed, plus im in no rush with this project so i can take my time. Im thinking i may rewire it with the same setup as it has now, and since i do want radio, a/c, etc. ill probably but a kit and add to it when the build starts getting more serious. Thanks guys.

Originally Posted by glennsexton

You may want to contact Painless or Keep It Clean
Painless Performance: The Official Home Page For The Best In Automotive and Diesel Performance Products
Automotive Wiring, Lighting, & Electrical Accessories || Keep It Clean Wiring

Both of these companies specialize in replacement wiring harnesses and all of the associated components. It's a lot more difficult to "re-wire" than it would seem on the surface (it's just a bunch of wires - right?)..

Welcome to CHR
Glenn

ill probably look with them when the project gets more involved and i start switching stuff. Right now its the original wireing so there is no radio, no a/c, nothing extra so its pretty straight forward, so im thinking it wont be to bad if i take my time.

Heres my thoughts. Any wiring will eat up lots of time,so I only want to do it once.
In 1940 they did not use fuses so none of the circuits are protected. So I would by a 20 circuit wiring kit so that you have circuits for any thing you want to add down the line,you can simply tuck unused wires behind a kick panel. Change all the bulbs to 12 volt,I would use a G.M. alternator,you will have to fab brackets for it.your 6 volt starter will work fine.Painless and others sell a converter that you can install to make your 6 volt gauges work.Swap the 6 volt ign.coil to a 12 volt and install a ballast resistor.All of your stock switches should work fine.

thanks HWORRELL, i think that's the path i may take now plus i wont have to do it twice which would be nice. What gauge wires would u recommend using, should i just use the same gauge wire that is there now.

14 and 16 gauge will work on most of your circuits except for alternator and amp gauge and I'd go with 12 gauge. Make sure you have good clean grounds and I'd probably replace the dimmer switch with a new one. I rewired a 36 5 window coupe in the 60's in that manner.