1952 M38 converting to 12V

[Ryan0186]

Good morning,

I have a 1952 M38 that i am currently completing a frame up restoration on. The Jeep currently has the 24V system. For project budget reasons I would like to convert this one to 12V. Appears that the 12 volt parts are about 1/4 of the cost. This will not be a show Jeep, just a weekend cruiser. The 24v starter is currently not working at 100 percent and I am unable to confirm if the generator is also functioning properly. The entire 24V harness had to be removed due to years of others hacking into it, rodent damage, and overall degradation due to age/elements. The gauges and all electrical fuel components are also going to need to be replaced. Basically I am starting over from scratch. My question is when converting over to an alternator how do you handle the dual belt system and wiring it into the M38 12V harness sold online. I am assuming I would need to find a way to swap the dual belt generator pulley onto the new alternator? Also I am planning to just swap in a 12V coil and use the existing water proofed distributor and wires. I know some will read this and say it’s pure blasphemy to even discuss converting it, however the budget and time don’t dictate me being able to do a proper restoration of the original 24V system. Any input y’all can provide is greatly appreciated.

[Xamon]

This is a relatively common modification. pretty sure there are many discussions here somewhere.

For the pulley you can swap it but really if the single pulley lines up with one groove and is of the same size you can run it with just one belt to the alternator. Or at least that is my opinion and I have seen commercial systems that run one belt to the alternator and a separate one to some other accessory.

[wesk]

The first time I did the 12V conversion was to a 1954 M38A1 while I was still in the Air Force and stationed in SD.

This is the first M38A1 I owned in 1986 and converted to 12V, civvy vinyl top and nice 10" wheels and tires.


This is the Harness and fuseblock used. Note starter, generator, lamps and gauges are not included.


Please note that I relocated your technical question from the Projects Board to the Technical Question Board. The project board is for folks who wish to post their daily/weekly progress on their projects to share with other project owners or folks interested in seeing just how much time, effort and money goes into these projects.
It is quite simple. Get youself a copy of the 1962 CJ parts manual or visit it here in my photo album. You will simply swap all your 24 volt stuff for a 1960 CJ5's 12 volt stuff. This includes the 1960 CJ5 fuse block assembly. Most of this stuff is readily available with most of our current jeep parts vendors. There are a few areas you must tread lightly and carefully in.

1 - Turn signals. Choices are a full conversion to the 1960 CJ5 or an aftermarket column mount turn signal selector.
2 - Instruments. Best bet here is simply replacing the 4 cluster gauges with commercial aftermarket gauges including the aftermarket senders where used. For Oil pressure and water temp I prefer the direct type gauges. No electric sender for the oil pressure and a simple heat activated capillary type water temp. If you shop one manufacturer's stocks you can keep the appearance of all 4 very close to each other.
3 - Ignition. There are several solutions here. If stock factory appearance is not paramount then modernize and go with a stock 1960's CJ5 or aftermarket 1960's CJ5 system. The shielded harnesses and plugs are current priced off this planet and won't perform any better then the stock or aftermarket non-waterproof systems.
Be sure to utilize my photo albums:

12 V conversion to ignition
http://www.willysmjeeps.com/v2/modules. ... _album.php

M Series Electrical
http://www.willysmjeeps.com/v2/modules. ... _album.php

M Series Lighting
http://www.willysmjeeps.com/v2/modules. ... _album.php

M Series Ignition Systems
http://www.willysmjeeps.com/v2/modules. ... _album.php

http://www.willysmjeeps.com/v2/modules. ... um.phpTurn Signal Choices

The CJ5 service manual that will cover the year group CJ5 electrical you are switching to
http://www.willysmjeeps.com/v2/modules. ... _album.php

The 1962 CJ Parts Manual
http://www.willysmjeeps.com/v2/modules. ... _photo.php

The 1967 CJ parts manual
http://www.willysmjeeps.com/v2/modules. ... _photo.php

The Chilton CJ service manual:
http://www.willysmjeeps.com/v2/modules. ... _album.php

Since I am an Aircraft mechanic by trade with a long history of car racing (back to 1959) and Jeep restoring (back to 1971) I have acquired many other manuals that are a great help with these projects.

Here's a favorite from the FAA that you can download free from their web site:
http://www.willysmjeeps.com/v2/modules. ... _album.php

Alternator adaptation to the F134 generator mount can be done several ways. Just google up a ton of choices at:
https://rb.gy/2px8mp

As for make.model alternators your accesibility and funds will narrow that choice down for you. Although one wires are nice they are also normally more expensive and repairs for just a regulator portion failure are not cheap. My preference is the Old Reliable Ford 60 amp 12V alternator with a very inexpensive remote mount voltage regulator.

So in summary I suggest you start your conversion with the mentality that you want an end product that will give you no grief and will be reasonably priced. Second you set down and review all data before making choices. Third you follow the applicable manuals and drawings as you start the modification work.

[RonD2]

I thought the trickiest part was finding a good alternator mount. There's some junk mounts on the market.
I'm using the common "one wire" Delco 10SI alternator with a low-rpm cut-in 13.8v set point regulator.
I put a 2 belt pulley on it and it lines up with the crank and water pump pulleys nicely.
Have to look through my notes, but can send links to my sources if helpful.

The conversion isn't hard to do --- assuming you have some knowledge and experience with automotive electricity.
If you don't you have some study to do to avoid smoke and fire, and most of the folks that are active in the forum are willing to offer advice.

There's a member in another thread that's converting back to 24v from 12v and he's looking for parts (starter, generator, gauges, etc).
A match made in heaven.

Good luck!

[Ryan0186]

Thanks everyone for the helpful advice. It’s going to be closer to the end of the year before I start buying more parts, so plenty of time to research. I’ll take a deep look through everything that y’all have provided. Thanks so much

[Ryan0186]

Does anyone have a vendor they can recommend that sells a 12V coil that will fit inside the waterproof distributor housing?

[wesk]

Take a look at this photo album that shows the process one of our members used for an internal 12 V coil substitution: http://www.willysmjeeps.com/v2/modules. ... _album.php

Here are links to his two project related 2014 posts: http://www.willysmjeeps.com/v2/modules. ... dification
http://www.willysmjeeps.com/v2/modules. ... dification

[RonD2]

OP has a M38.
I assume it has a L134 engine.

[wesk]

He is better off using the CJ5 12V harness and fuse box then the older incorrect wire gauge CJ3A 6 volt.

[RonD2]

I haven't seen his jeep (or photos) and don't know exactly what he's dealing with, but yes, I agree, there's lots of options.
Especially since he said:

Basically I am starting over from scratch.

[Stiknruddr]

I used a 1 wire GM 2 pulley alternator bought off Epay and a bracket from Willys works. Bolt on. Purchased a nos main wiring harness for a M170 (cheap) from one of the parts suppliers, purchased several unknown harness same wire gauge from relay cheap some connectors from Saturn surplus built the secondary harnesses. Fused the main power feed. Yes it’s twice the amperage but I haven’t had any problems. However….the later 3 lever light switch has an internal circuit breaker that will trip using 12v. Just open it up and bypass (remove) it.