m38a1 wiring harness

zeke57 · Post by **zeke57** » Fri Dec 29, 2017 11:24 am

Hi I am a new member and am looking for some help rewiring a 52' a1 for 12v and am needing some direction on how to proceed. Thanks.

Post by **wesk** » Fri Dec 29, 2017 11:30 am

You have several choices. Which you use depends on your personal desires and your expertise with electrical systems. We would need to know these things to be able to offer you any sound advice. We would also need to have a list of all your jeep's electrical components.

1-Just order an aftermarket 12 volt CJ5 harness for a 55-71 CJ5.

2-Modify your military harness to serve your new 12 volt equipment. (This is a dangerous course and requires a very strong working knowledge of automotive electrical systems. Age of current wiring can cause serious problems.)

3-Design and fabricate your own harness. (This is the toughest choice and again requires a very good working knowledge of automotive electrical systems.)

zeke57 · Post by **zeke57** » Fri Dec 29, 2017 6:35 pm

I am in no way an expert on electrical issues but I think I could comprehend what advice you give me. So what I am dealing with is a a1 I purchased minus the original engine but I have been able to find a f134. I would like to do a 12v conversion and be able to be road legal. I thought about a 24v restoration but I lack most of the underhood components. So right now I lack 12v alternator but I do have a 12v starter 24v gauges still in place no tail lights no blinkers. I have purchased some aftermarket 12v gauges and headlight switch. I very much appreciate the reply wesk, thanks. I think the cj harness sounds like my best option.

zeke57 · Post by **zeke57** » Fri Dec 29, 2017 6:57 pm

Forgot to ask previously why a 55-71 harness is required just asking because I know where I can acquire one from an early 80' cj.

Post by **wesk** » Fri Dec 29, 2017 11:43 pm

The 55-71 matches the M38A1 body dimensions and equipment layout and engine model. 1972 & up were longer, used the AMC in line 6 and V-8s as well as the Chevy 4 cyl. in the 80's.

You should go with mechanical water temp & oil Pressure gauges. Or you can shop for a CJ5 round instrument cluster. It is quite easy to fabricate a flat steel or aluminum rectangular panel to fill the military gauge pane and fit the CJ round dial gauge set. Keep in mind that although 12 V systems were available for the 55-57 CJ5 they were optional to the standard 6 V system. 1957 made the 12 V system standard.

You can adapt a civvy 12V fuel sender to the M38A1 tank but you must match the civvy sender to a civvy gauge.

The CJ5 came with a 6V or 12V DC generator thru 1962 or so when it adopted the 12V Motorola alternator. Don't bother looking for one of those. Just get a standards Delco one wire alternator with a built in regulator. There are alternator mount adapters on the market.

Let us have a complete final list of 12 volt components with PN's or Model #'s when you are ready to start. Also post a photo/photos of the new civvy wiring harness detailing it's terminal ends and a scanned copy of the wiring diagram that came with it.

You will want to shop for a copy of the CJ5 service manual SM-1046 and the CJ series Parts Manual 1962 or 1967 editions W-1103. The 67 edition covers the V-6 engine installation for the CJ5/6 66-71.

SM-1046

W-1103 1962

W-1185R1 1967 Includes V-6

Be sure to use my photo album with hundreds of technical photos that answer 80% of the questions asked on these boards.

zeke57 · Post by **zeke57** » Sat Dec 30, 2017 8:06 am

Yes my water and oil pressure gauges are mechanical and I also have a jeep service manual form sm-1002-r6 printed in 1965 or do I still need to find the manuals that you mentioned. Could you suggest where to look for a wiring harness and roughly what I should expect to pay? Thanks again.

Post by **wesk** » Sat Dec 30, 2017 9:34 am

To give you a perspective, the replacement new manufacture military harness's are running over $780. The civvy aftermarket new manufacture harness's are $200 to $600. This is a parts class where you get what you pay for!

Painless Products top shelf $519. 1942-1974 CJ

https://www.quadratec.com/products/2701 ... AEQAvD_BwE

Link to Painless Harness Install Manual: https://www.quadratec.com/sites/default ... /11840.pdf

American Auto Wire $251 Universal 12V kit.

https://www.summitracing.com/parts/aww-510004/reviews/

Kaiser/Willys custom M38A1 12V conversion harness. $315
I do not see a fuse box with this harness and again this is a one size fits all harness.

https://www.kaiserwillys.com/category/e ... a1-12-volt

The SM-1002 is a good manual for the civilian side of the m38 and helpful for the A1. I prefer the SM-1046. I have both and when I look for 60's vintage jeep data I grab the 1046 first. If a V-6 is not in your future then the early parts manual is adequate.

zeke57 · Post by **zeke57** » Sat Dec 30, 2017 5:34 pm

I was looking through the jeep manual that I have and I did not see a fuse block on the wiring diagram. I wonder if they had them back then is that maybe why the Kaiser/Willys harness does not have one in the picture. I was on Walck's site they also offer one also but again no fuse block in the picture I am going to call them on Tuesday for more info. The AAW from Summit also looks like a possibility it seems to have good reviews.

Post by **wesk** » Sat Dec 30, 2017 9:20 pm

Most M38's had 3 circuit breakers behind the dash and early M38's had a fourth on the back side of the instrument cluster. The military decided it was more important to keep her running then it was to protect individual circuits so they dropped the CB's. The only CB on the M38A1 is inside the main light switch.

Trust me when I say everything I rebuild gets fuses or CB's to protect the circuits. It is a very foolish move not to use them.

The main light switch is another dilemma you will face. Drop it and use a modern pull switch and you have a empty very large hole in the dash. Try to adapt it to any aftermarket harness is a tough task but doable.

zeke57 · Post by **zeke57** » Sun Dec 31, 2017 8:16 am

Your advice is well taken I will definitely use a fuse block. I do have a pull light switch that I will be using and my plan is to just leave the old military light switch in place or is there a reason to remove it? So your opinion on the AAW harness at Summit? Looks like a good way to go to me.

Post by **wesk** » Sun Dec 31, 2017 10:02 am

I've always scratch built my own harnesses so I have no exposure to these aftermarket harnesses. I would suggest canvassing known purchasers of each harness you are considering. Since the bulk of our members are stock 24 V users you may need to visit other on line boards for 1940-1960's classic car & truck restorer's opinions. If their advertising is above board then it appears the AAW harness gives the best bang for the buck.

Leaving the military light switch in place does no harm. If I were restoring that jeep and IF I was using the stock light assemblies front & rear I would adapt the military light switch to the civvy harness. If I was using the jeep as a driver I would include turn signals.

The early single plug Bendix-Scintilla military light switch would be the best choice to adapt.

The one in the middle

The switch is not as complicated as it appears.

All of this really depends on what you plan for your jeep and how you plan to use the jeep. My first M38A1 I bought in South Dakota in 1986. It was a 24V stock driver owned by Pennington County Civil Defence. In true to newby fashion I converted it to 12V using the original military harness.

This is my first M38A1 in South Dakota 1986

zeke57 · Post by **zeke57** » Mon Jan 01, 2018 8:17 am

My intentions for this jeep is to make it a driver and I have a lot of work to do basically I bought this without a driveline and cobbled together wiring missing this and that. So right now I am focusing on the harness. I have noticed the harness that Kaiser/willys offers is pre-terminated so that would be a plus but on the down side no fuse box so I guess the question is can I add a fuse box or am I better off with the AAW harness and install my own terminals?

4x4M38 · Post by **4x4M38** » Mon Jan 01, 2018 9:07 am

Bretto built a harness basically paralleling the
24 volt M38 harness but with a 12 volt vehicle,
Including a fuse block, circuit breakers and turn
signals.

Post by **wesk** » Mon Jan 01, 2018 12:14 pm

zeke57, as you have already indicated you prefer the aftermarket ready to install harness and not the more difficult self fabricated harness or repaired/modified GI harness. With this in mind the Aftermarket harness with a fuse block is the way for you to go.

zeke57 · Post by **zeke57** » Thu Jan 04, 2018 11:59 am

Think I am going with the universal wiring harness made by Rebel wire in TN. it seems to be good quality and their product support is great.