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keithb7

80 Yr Old 6V Electrical Wiring Questions

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I have some electrical questions related to my ‘38 Plymouth. 

 

My car appears to have had its share of questionable wiring work done to it over the past 80 years. I’m looking at it and trying to come up with a repair plan. I have a few questions:

 

There are several wires pulling 6V right off the starter lug. The horn, the headlights, to name a couple.

 

I also see 6V beeing pulled off the ammeter  gage rear lug. There’s a cab heater fan and an electric fuel pump pulling from here. I suspect these will pull the ammeter gage down when pulling current. 

 

What about the 6V being pulled right from the starter cable lug? When these circuits are on will they too show amp draw on the ammeter? 

 

I am thinking the stack of wires mounted to the rear of the ammeter could be cleaned up. Perhaps a busbar instead? A distribution from a central point mounted away from the ammeter. With larger 1 wire going to the ammeter?  

 

Or maybe I should have all these accessories moved down to a buss bar off the starter lug? Then have 1 wire pulling off the battery to the buss bar? Then all accessories pulling off the busbar? Add fuses to protect all?

 

I’m thinking I’d rather be safe versus building a concours car. 

 

Thanks. 

 

 

 

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Thinking in modern terms you have ignition on accessories, and ignition off accessories, or those items you would like off when the key is off and removed.  In what you just described, things like head lamps, horns, brake lamps, courtesy lights, trunk or under hood light would operate with the key in either position.  Radio heater fan fog lamps, fuel gauge, cigar lighter, accessory fans, signal lights,  you would want off when your shut down the car or alternatively powered by the accessory terminal on the ignition switch. Picking up power from the starter lug if it's hot all the time would be you ign off feeds, the ammeter out terminal would be your "ignition on" feeds if you don't want to use the ignition switch run and accessory terminals if your switch is so equipped. The voltage regulator is what senses the load and triggers the generator output to maintain battery voltage at the charged level. Also if you are re wireing and keeping six volts, use thicker wires than for 12 v.  Use 10 gauge for heavy loads, 12 gauge for medium, and 14 for light loads.  16 gauge or lighter wire has no place ( ok maybe the dash lights) in a six volt vehicle.

Edited by greg g

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I wired my truck two times, fire destroyed the first job, by trying to follow the schematics, took me forever. Then I put a 12 volt kit harness in my current Suburban that also took a lot of time. 

 

Now I have one more to do, a ‘53 coupe. This time a good friend will help and we will pull and replace the wires, one at a time. We will unwrap a section, rewire the rewrote, etc. and will crimp and solder each end as we go. Probably take us a day maybe two. 

 

Photos not my car. The black one may be a Dodge.

 

 

C6C9DE41-D646-465F-866C-07E890BAACBB.jpeg

Edited by pflaming

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11 minutes ago, pflaming said:

I wired my truck two times, fire destroyed the first job, by trying to follow the schematics, took me forever. Then I put a 12 volt kit harness in my current Suburban that also took a lot of time. 

 

Now I have one more to do, a ‘53 coupe. This time a good friend will help and we will pull and replace the wires, one at a time. We will unwrap a section, rewire the rewrote, etc. and will crimp and solder each end as we go. Probably take us a day maybe two. 

 

Photos not my car. The black one may be a Dodge.

 

 

C6C9DE41-D646-465F-866C-07E890BAACBB.jpeg

not likely.....it has Cranbrook script...….try one a 53 (black betty) and the other a 54 (blue bomber) the black is a club coupe the blue is a sedan...the rear window divider tells the story...

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Then mine is a coupe. Aside the window post, what are the other differences?

 

The club sedan and business coupe shared the same general body details, the club sedan having a rear quarter window while the business coupe had a solidly fixed rear side window. Business coupes came without a rear seat and the option of carrying the spare tire in the trunk or rear compartment. An optional rear seat cushion could be ordered to turn the vehicle into a family car on weekend while still retaining its business capabilities during the week

1EED83FD-D20E-4111-A1D4-B5D1C9FADD62.jpeg

Edited by pflaming

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Second what Greg g wrote. Just want to add the following: fuses, fuses and then some more fuses. Specially dome light.

On most older cars, dome lamp are wired hot. Some as a turn switch, others as door switch. They go through a flimsy bi metal fuse at rear of light switch. Don't  rely on it, use a traditional fuse. If it short circuits, wire along head lining, car will burn down.😩 

If you don't like your ammeter, install a bulb between Arm and Bat on regulator and presto, you have a modern charge lamp.

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I agree with, chrysler1941 - fuses are required for safety. Where the insulation and general condition of  existing wiring is acceptable and a 100 percent correct restoration is not required,I have used couple of items to improve safety of the electrical wiring.Normally,I  would disconnect the battery if it is easily easily accessible and the vehicle is left unattended for any length of time.

On my 1936 DeSoto coupe, I replaced the cable from the battery to the starter and also the ground cable.Because the battery is located under the seat, for convenience the wire from the starter to the rest of the vehicle is through a fuse to a disconnect switch as pictured.

On my 1937 Chrysler,the battery had been relocated to the trunk by a previous owner, I disconnect the battery when not in use. I used an insulated standoff as pictured on the firewall as a tie in point to fused wiring to the rest of the car.I used heat shrink to cover the stud when I finished making the connections.

These parts are easy to find.

Not stock but easily corrected if someone wants to go that route in the future..

1182502591_1936DeSoto.JPG.7a51eb52e3562c0501d33defe05f58e6.JPG

 

 

Insulated junction block.jpg

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I agree on the fuses. I plan to install them.  Good point on the different circuits working with key switch  on or off only. 

 

The wiring layout is in my shop manual, but there is not actual schematic. I’d like to see a proper schematic.  @T120 are you able to post more photos of the wiring in your ‘37 Desoto? It appears mostly the same as my ‘38 Ply. Your pics will help give me some ideas on layout.  I’d overlooked a master on/off switch until now. I do like that idea. I will consider it. For now I’ll remove a  battery cable. 

 

I am using 12 ga and 14 ga wire at a minimum. I agree 100% on the 6V system needing more amp flow. 

 

 

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 I scanned the wiring diagram and harness for the 1937 Plymouth,it may be of some use...With my 1937 Chrysler a previous owner had converted it to 12 volts and relocated the battery in the trunk. There was also a number of wires that were connected at the starter,I moved them to an insulated terminal on the firewall and added some fuses...

1849843443_1937Plymouthwiringdiagram.jpg.7d7abbe5d7ca0b2299c7606f68cbe210.jpg1782773036_1937Plymouthharness.jpg.f7ed48aead6081dbcfa4b445f331a959.jpg

Edited by T120
spelling

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Thanks @T120. I have the same wiring info in my 1938 P6 original shop manual.  I see what you’ve done there with the lug, to get the wires off the starter lug.  In-line fuses look good there.  I appreciate the effort to add info and pics here. 

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5 minutes ago, keithb7 said:

Thanks @T120. I have the same wiring info in my 1938 P6 original shop manual.  I see what you’ve done there with the lug, to get the wires off the starter lug.  In-line fuses look good there.  I appreciate the effort to add info and pics here. 

I won't brag about the workmanship. As I wasn't aiming for a full restoration,I just addressed some weak points in the wiring at the time and it gave me confidence to connect the battery and turn the key on.. 😊

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@T120 that’s where I’m at. Fix up some bad wiring. Make it reliable and start enjoying the car. Then progress from there. I may be back in the wiring in a few years but I’m not concerned. 

 

I can understand the comments to replace all the wiring and harnesses.  Someday I likely will. Not yet. I want to get the car running and driving so I can assess the rest of it. Then plan the work I’ll do. 

 

Thanks for everyone’s comments. I’ve got some ideas now to move ahead. 

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On my 1937 Chrysler, I'm kinda embarrassed of the photo I  posted of the wiring I did around the starter motor... When I bought the car several years ago ,a previous owner had the car into a shop and paid to have it converted to  a 12 volt negative ground battery system...while some of the work they did was okay,I  wasn't happy with the cluster of wires at the starter motor.. After I bought the car, .I did a rather quick assessment of the wiring and this was basically what I did one evening to give me some peace of mind ...It was rather a quick and nasty fix..

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After studying the stock wiring layout and proper relay wiring, then comparing it to the actual wiring in my ‘38 today I can see that  I’m working with a real interesting rendition. 

 

Relays are wired up as anchored butt-connections. There is no horn relay. 6V right off the battery straight to the horn. The horn button grounded, with no fuse, gets all the amps it can take.  The hi/lo beam switch...I’m not sure I can describe how it was hooked up. It was totally ineffective.  Add to that all the bare exposed wires, overlander, and cut wires, it truly is a miracle the car did not burn up. 

 

I haven’t even gotten serious about the wiring up under the cowl yet. 

I am happy to fix this up and keep the car alive. 

 

Edited by keithb7

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In some cases because of the age of the wiring - with brittle insulation as well as corrosion of the conductor, point to point replacement is the only solution.

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Agreed. I’m finding the old wiring is quite corroded under the cloth covering. Soldering to it becomes futile. 

 

Is it ok to place my head light relay before the hi-low beam switch? I think I’d rather not use 2 relays, (1 for each hi, and low beam circuit). 

The hi/low beam foot switch seems like it might be robust enough to handle the amp draw via the relay. Is it?  Thx. 

Edited by keithb7

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Both switches are robust enough to handle the current for stock wattage headlights, since that's how they were designed to work, as long as the contacts are clean and the wiring isn't adding more resistance (load).

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3 minutes ago, Merle Coggins said:

Both switches are robust enough to handle the current for stock wattage headlights, since that's how they were designed to work, as long as the contacts are clean and the wiring isn't adding more resistance (load).

 

Thanks Merle. The stock headlamp system was upgraded to 6V sealed beams some time ago. I believe these pull more amps. I’ll go with 1 relay before the  hi-low beam switch. 

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I had a problem with the headlight switch on my 1936 DeSoto.There was some resistance to pulling out the switch to operate the lights and it was not making proper contact.I removed the switch and found the phenolic portion of the switch was slightly warped and discoloured and it looked as though it had overheated sometime in the past.I was able to carefully disassemble the switch, cleaned and lubricate the contacts and reassembled it and the switch now works okay . I was able to find a N.O.S. light switch as a spare .

My 1936 DeSoto is also 6 Volts,and the headlights had been changed to sealed beam lamps. I plan to wire in a 6 volt dual headlamp relay. I found this one on ebay cost was around $30.US.

It is a K-W stock no C -1080 ( N.O.S.,made in U.S.A.)....See figure 1 on the diagram

1668213637_K-WDualHeaadlightrelay(2).thumb.jpg.b95b9038042d99d6a4babe3ce0a1a463.jpg1871534300_K-WDualHeadlightrelayno.C1080(2).thumb.jpg.f4b81c87ff8e2d65d28de12ef855f7f6.jpg1188456637_K-WRelayDualHeadlightInstallation(2).jpg.00fc8ed279d0619fe5882acda058946d.jpg

Edited by T120
added text

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Just an FYI, one reason the factory had for stacking a bunch of connections on the starter, for one example, was to save 6&13/16” (or whatever) of wire in the manufacturing process. A nickel, a nickel there. It adds up to BIG bucks for the factory.

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@T120 I like that double relay. A good solution.  For now I will try a single relay before the hi/lo beam switch. It if gives me trouble, I’ll be back here to get the info for that double relay.  Thanks for your posts here. They’ve been helpful. 

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