1947 p15 sedan 12 volt conversion

[al3xcooktattoos]

Hey all, I just acquired a 47 p15 sedan and I’m working toward making it a semi-daily driver. I’ve already got an entire new cooling system on order, and I’m doing the brakes next week.
 
anyway, I want to do a 12v conversion, and I’m wondering if any of you have an affordable kit to recommend.  It seems like I can find anything from a wire harness with an alternator for a couple hundred bucks on up to the full kit for just under 1k.  
are the kits even worth it? Or should I just go grab an alternator and starter solenoid and go for it? what else would I need if I went at it on my own? Do I need to do anything involved to switch to negative ground?  Any tips are very much appreciated!

3 speed manual if that makes a diff by the way

thanks!

alex

[Sam Buchanan]

A healthy 6v system works very nicely for a daily driver. Only real reason for 12v is if you want to use 12v accessories. But the absolute first thing you need is one of these:

 

https://www.rockauto.com/en/moreinfo.php?pk=10593924&cc=1486874&pt=10335&jsn=374

 

 

Welcome to the community and enjoy your new ride! 

Edited April 26, 2023 by Sam Buchanan

[al3xcooktattoos]

3 hours ago, Sam Buchanan said:

A healthy 6v system works very nicely for a daily driver. Only real reason for 12v is if you want to use 12v accessories. But the absolute first thing you need is one of these:

 

https://www.rockauto.com/en/moreinfo.php?pk=10593924&cc=1486874&pt=10335&jsn=374

 

 

Welcome to the community and enjoy your new ride! 

Thanks so much for the link! Definitely ordering one now. 
The main reason for the 12 b switch is I’ve  already ordered an electric wiper motor that runs on 12v, but I’m definitely open if there’s a way to run it on the 6 v system.  Not sure if the vacuum system is running correctly right now. The wipers run slower the faster I go, and only ramp up when I let off the throttle.  that’s just not going to cut it in the Pacific Northwest. ?. I also figured it would open up the world to me as far as getting a jump from a stranger in a pinch without blowing up my battery.  
thanks again for the response!

 

[Sam Buchanan]

Looks like your vacuum wipers are working normally.......they are driven by intake vacuum which is greater when the throttle is closed and reduced with open throttle. Some owners install a vacuum accumulator which stores vacuum for a steady source and there may be a fuel pump for your car that incorporates a vacuum pump. I suspect a 6v motor is an option, maybe someone on the forum can supply that info. An alternator will keep your battery topped up and make for reliable starting without the maintenance requirements of a generator and regulator.

 

You're just starting your old Mopar journey, you will eventually come to appreciate the wonderful engineering in these old cars.

Edited April 26, 2023 by Sam Buchanan

[Los_Control]

Sounds like you plan a new wire harness. The first thing would be to evaluate the condition of your harness.

If it is original cloth covered .... probably needs replaced.

If it has been replaced already & still 6 volt & in good condition .... will work fine for 12 volts.

 

I think 12 volts does have advantages. Big reason for me is to do the slant 6 distributor hack to get oem electronic ignition.

Points & condensers are hit and miss today with overseas quality parts.

Yes you can still use 6 volt pertronix ..... I prefer oem available from any local parts store.

 

Myself have not done the conversion yet. I chose what I thought was a Chevrolet internally regulated alternator. ...... Ended up with a externally regulated one.

No big deal, $20 more for the regulator & I have to rewire it all anyways.

 

I have it hanging on the upper bracket to size it up. Biggest problem I see is fabricating the lower bracket.

Everything needs to move forward 3/4" to line up the pulleys. ..... this is where a kit would be handy, the mounting brackets are taken care of.

The upper bracket can be heated & bent in a vise .... The lower bracket will be easy, just a zillion different ways to do it.

 

So that is my view ..... A kit is easier installation.

My way, have to fabricate mounts .... alternator is available at any parts store. Think I paid $48 for the 65 amp alternator, $20 for a solid state voltage regulator.

If I was smarter, I would have bought the internally regulated alternator for the same $50 & saved $20.

[Sniper]

Having converted my 51 to 12v, don't forget all the bulbs need conversion as well as the battery.  You will also need a 12v coil and a ballast resistor. 

 

When  added the alternator I simply use the alternator and regulator from an 87 Dodge Diplomat.  I was able to use some all thread, washers for spacers and nuts to fit the alternator to the original generator bracket.  Mounting link  Regulator connector link Field connectors Regulator Alternator Ballast resistor Coil

 

Regulator and ballast as installed

 

 

I also used a 4 terminal Ford application 12v starter solenoid and bought new battery cables, don't forget to change the red from the block to the starter circuit.  The fourth terminal on the starter solenoid is wired to bypass the ballast with the key in start (ignition 2 in schematic).

 

Regulator and ballast schematic. The BATT on the alternator is the threaded stud that goes to the ammeter (switch your ammeter leads so it read correctly).  The blue and green lines can go to either field spade terminal on the back of the alternator but the should go where labeled on the regulator.

 

 

I rewired the whole car as the original harness was falling apart.  Used a generic 22 circuit kit from Speedway.

Edited April 26, 2023 by Sniper

[rockingjd]

I know it's pricey but I liked the look of the alternator from Power Master. Looks like a generator charges like the alternator. Single charge wire no external voltage regulator.

 

I didn't wire in the amp gauge but did add a volt gauge.

 

[al3xcooktattoos]

On 4/26/2023 at 6:05 AM, Sam Buchanan said:

Looks like your vacuum wipers are working normally.......they are driven by intake vacuum which is greater when the throttle is closed and reduced with open throttle. Some owners install a vacuum accumulator which stores vacuum for a steady source and there may be a fuel pump for your car that incorporates a vacuum pump. I suspect a 6v motor is an option, maybe someone on the forum can supply that info. An alternator will keep your battery topped up and make for reliable starting without the maintenance requirements of a generator and regulator.

 

You're just starting your old Mopar journey, you will eventually come to appreciate the wonderful engineering in these old cars.

Well no matter what these vacuum wipers do, I love this thing.  I can’t wait to give it the love it deserves. I’ve never had so much room to move  around in and engine bay! It’s almost like I can turn wrenches without bloody knuckles..  Wishful thinking I know! 

[blue p15]

Oh, the joys of vacuum wipers!  Most 12volt wipers that I have seen cannot be used with the original radio because of clearance issues.  You might be able to find a 6volt motor from an early 50s Mopar that would work.  If your wires are in good shape, the 6volt wiring will be heavier than a 12volt replacement harness.   My personal opinion is that modern plastic coated wiring looks out of place on these cars.  A good cloth covered wiring harness is going to be more expensive than a 12olt replacement, but I think it would be worth the extra cost in the end.  Just my two cents worth!!  Enjoy your great car!!

[Doug&Deb]

Post war Dodge used electric wipers. That may be an option for you.

[al3xcooktattoos]

On 4/26/2023 at 8:19 AM, Los_Control said:

Sounds like you plan a new wire harness. The first thing would be to evaluate the condition of your harness.

If it is original cloth covered .... probably needs replaced.

If it has been replaced already & still 6 volt & in good condition .... will work fine for 12 volts.

 

I think 12 volts does have advantages. Big reason for me is to do the slant 6 distributor hack to get oem electronic ignition.

Points & condensers are hit and miss today with overseas quality parts.

Yes you can still use 6 volt pertronix ..... I prefer oem available from any local parts store.

 

Myself have not done the conversion yet. I chose what I thought was a Chevrolet internally regulated alternator. ...... Ended up with a externally regulated one.

No big deal, $20 more for the regulator & I have to rewire it all anyways.

 

I have it hanging on the upper bracket to size it up. Biggest problem I see is fabricating the lower bracket.

Everything needs to move forward 3/4" to line up the pulleys. ..... this is where a kit would be handy, the mounting brackets are taken care of.

The upper bracket can be heated & bent in a vise .... The lower bracket will be easy, just a zillion different ways to do it.

 

So that is my view ..... A kit is easier installation.

My way, have to fabricate mounts .... alternator is available at any parts store. Think I paid $48 for the 65 amp alternator, $20 for a solid state voltage regulator.

If I was smarter, I would have bought the internally regulated alternator for the same $50 & saved $20.

I will most likely do the full wire harness. It’s looking like all original fabric wrappedwiring as far as I can tell and brittle and beat is the least i can say! the electronic ignition is a definite bonus. 
the kit I’m looking at has all the brackets and pulleys that line up so for ease of install I’m most likely going that way. 
Very tempting to save the dough and just get a generic harness and alternator.  

[al3xcooktattoos]

4 hours ago, blue p15 said:

Oh, the joys of vacuum wipers!  Most 12volt wipers that I have seen cannot be used with the original radio because of clearance issues.  You might be able to find a 6volt motor from an early 50s Mopar that would work.  If your wires are in good shape, the 6volt wiring will be heavier than a 12volt replacement harness.   My personal opinion is that modern plastic coated wiring looks out of place on these cars.  A good cloth covered wiring harness is going to be more expensive than a 12olt replacement, but I think it would be worth the extra cost in the end.  Just my two cents worth!!  Enjoy your great car!!

I was actually looking at cloth covered harnesses last night! They definitely seem few and far between. I definitely agree that the plastic coated wires clash with the whole vibe of this thing.   I’m still probably going that route but I’m definitely wrapping all of it in fabric loom so I don’t have a bunch of plastic showing.  
cheers!

[al3xcooktattoos]

On 4/26/2023 at 12:13 PM, Sniper said:

Having converted my 51 to 12v, don't forget all the bulbs need conversion as well as the battery.  You will also need a 12v coil and a ballast resistor. 

 

When  added the alternator I simply use the alternator and regulator from an 87 Dodge Diplomat.  I was able to use some all thread, washers for spacers and nuts to fit the alternator to the original generator bracket.  Mounting link  Regulator connector link Field connectors Regulator Alternator Ballast resistor Coil

 

Regulator and ballast as installed

 

 

I also used a 4 terminal Ford application 12v starter solenoid and bought new battery cables, don't forget to change the red from the block to the starter circuit.  The fourth terminal on the starter solenoid is wired to bypass the ballast with the key in start (ignition 2 in schematic).

 

Regulator and ballast schematic. The BATT on the alternator is the threaded stud that goes to the ammeter (switch your ammeter leads so it read correctly).  The blue and green lines can go to either field spade terminal on the back of the alternator but the should go where labeled on the regulator.

 

 

I rewired the whole car as the original harness was falling apart.  Used a generic 22 circuit kit from Speedway.

Thanks for the diagram!!! Cheers!

[Los_Control]

2 hours ago, al3xcooktattoos said:

the kit I’m looking at has all the brackets and pulleys that line up so for ease of install I’m most likely going that way. 
Very tempting to save the dough and just get a generic harness and alternator.  

Time is money, I have more time then money. Having the brackets already made is well worth it.

 

I read a review someone did on the cheap generic wiring harness's available.

His qualifications, He works at or owns a shop that builds Hot Rods .... he has used all of the brand name wiring harness & he could nit pic little things about all of them.

He had a project where he wanted to try one of the cheaper generic wiring harness ....

His end results was, The wire grade was acceptable, the fuse box will work .... he was satisfied with it for that project .... shop truck? He would use them again.

Not in a $50k Hot Rod, but on a project appropriate for the cost.

 

I bought a cheap $50 harness from Amazon .... I agree with the guy with what I have seen. It is decent wire, well connected to the box, not going to fall apart.

We can make this work dependably.

 

My issues with it would be different then yours. ...... I have a truck with a stomp starter (no starter system) vacuum wipers. Very basic wiring needs.

My goal was to de-pin the connectors from the box & wire it the way I wanted.

Cheap box, the wires are in there to stay .... thats a good thing .... unless you want to modify it.

It has 2 relays for turn signals & 4 way flashers ..... I can not use as is, can not move the wires around ..... I can cut, splice new wiring though.

The box is labeled with a sticker, ..... it is wrong & does not match the way the box is wired. .... pull the sticker off, the lid is stamped, I saw sun roof ... does not match our cars.

But the box & wiring will work. ..... You just need to pay attention & wire your car correctly, label as you go.

 

The fuses are so cheap, when I pull one out, they box is tight and grabs the prongs of the fuse ... the plastic fuse cover pulls off ... you need pliers to remove the prongs individually. ...... You need to replace the fuses with a known quality brand .... I imagine the relays also .... Box & wiring is solid though.

They have lots of wire .... I'm excited about that ..... Hard to buy that amount of different colored automotive wire for $50.

I'm cutting out my box, creating a custom box using the wire .... again can use as is.

 

Just saying, you can use the cheaper generic wiring harness .... you will need to work for it .... name brand will be easier.

I've decided I'm cutting the wire loose & building a custom fuse block I can modify as needed ....

If you can find a wiring harness made for your vehicle You are golden ... I personally will build one that fits me.