24 to 12 volt

circleburner12 · Post by **circleburner12** » Wed Mar 02, 2016 3:38 pm

hey guys been away for some time now. finally got the m38 to the point of either purchase a $800 wiring harness or changed to a 12 volt setup.
ive decided to go the 12 volt way. although i will keep 24 volt components.

my question is, is there a tuturial on changing from 24v to 12 v.

im sure this question has been ask a million times. but if anyone could point me to a step by step process with 12 volt part numbers, it would be much apreciated. thxs michael

Hawkshadow · Post by **Hawkshadow** » Wed Mar 02, 2016 4:47 pm

Go to the downloads section of the site. Under "electrical" there are several items that you should find helpful.

circleburner12 · Post by **circleburner12** » Wed Mar 02, 2016 7:05 pm

ok thanks i went therew but didnt find much. might have over looked it also,

Post by **wesk** » Wed Mar 02, 2016 10:16 pm

Just because you don't wish to buy an $800 harness is no reason to abandon 24 volt. You still need to build a harness either way 24 or 12. To do a nice job on either a 12 or 24 V harness will take about the same amount of time. If you are thinking 12 V but are keeping the 24 V components you may find that this will only make the task tougher. The military standardized with 24V in 1948 because it was a step up from 12 V. Now you are making a step down. 24 V accessories will not operate correctly with 12 V. Gauges will read incorrect values, the starter will turn slower, the lamps will be dim and the horn will be weaker. The 24V generator and regulator are useless on a 12 volt jeep.

If you are thinking buying a civvy CJ 12 V harness because it is cheaper then start shopping the ebay and surplus dealers for NOS Rio M35 harness for about $100 to $140 and adapt it to your jeep.

Here is the link to our copy of the US Forest Service pamphlet on 24V to 12V solutions.
http://www.willysmjeeps.com/v2/modules. ... it&lid=148

Here's the link to Novak's conversion guide:
https://www.novak-adapt.com/knowledge/12-volt/

4x4M38 · Post by **4x4M38** » Thu Mar 03, 2016 12:03 am

Yes there are alternatives to a new harness as Wes mentioned.
If that is all that is keeping you from staying 24 volts I would
try very hard to keep it 24 volts.

jaycee · Post by **jaycee** » Thu Mar 03, 2016 4:54 am

how you plan on doing this i'd be most interested in reading. especially the part about not changing any components save the harness! once you discover the flaw (s) in your plan that 800$ harness will seem to be a bargain at twice the price.

Bretto · Post by **Bretto** » Thu Mar 03, 2016 6:16 am

I'm guessing your saying your keeping the 24V comps but I would assume that to mean, keep on them on the shelf. It'll be a good amount of money to gather and replace them with their 12V counter parts.
I'm for keeping it it stock at 24V. If your existing harness or wiring is there, its a task but doable, to just trace out and replace wires one at a time. It's only wire after all.
Brett

skyjeep50 · Post by **skyjeep50** » Thu Mar 03, 2016 8:25 am

A 24v M38 will be worth more down the road than a 12v M38. What you save now, you may lose in the future.

OKCM38CDN · Post by **OKCM38CDN** » Thu Mar 03, 2016 5:20 pm

To convert to 12v you will need to acquire the following if you do not already have them:

New Gauges (all of them) possibly senders (can't remember if they needed changing too)
New lamps for all lights including headlights
New Starter
New Generator / Alternator
New Coil (if you have the Military Distributor there are 12v coils available, but they are expensive
If no coil available you may need to modify the distributor to get the coil connected... or a new distributor

I went from 12v to 24v ten years ago and it was a painful experience, but well worth the hassle of getting the jeep back to original...

If you do not want to spend $800 for a harness do your research and order the materials and build your own... most everything can be reused except for the pins on the wires and any rubber parts that may have dried out. The parts are available if you are willing to research where to get them...

The decision is yours to make, this is my experience in going from one to the other...

Good Luck and be patient...

Hope this helps...

Hawkshadow · Post by **Hawkshadow** » Thu Mar 03, 2016 7:40 pm

And even the crimped wire ends "can" be saved. It's just labor intensive involving drilling and soldering.

circleburner12 · Post by **circleburner12** » Thu Mar 03, 2016 9:02 pm

I understand that I have to change the components. the jeep wiring was almost completely gone. ive got a dist and trying to find a 12 volt starter. the part stores that ive checked with today cannot catalog a cj5 starter. wanting to keep the taillamps and replace bulbs. yes I understand the m38 will be worth more if I go back to 24volts. ill shelf store the 24v items incase I ever sell. thxs

4x4M38 · Post by **4x4M38** » Thu Mar 03, 2016 11:47 pm

M35 harness:
http://m.ebay.com/itm/M35A2-Wiring-Harn ... nav=SEARCH

Does not have the gen to reg cable but looks to have
nearly everything else.

aforests · Post by **aforests** » Fri Mar 04, 2016 11:10 am

4x4M38 wrote:M35 harness:
http://m.ebay.com/itm/M35A2-Wiring-Harn ... nav=SEARCH

I understand an M35 wire harness can be converted to fit a m38, but is a M35A2 harness convertable to M38 as well?

Post by **wesk** » Fri Mar 04, 2016 11:16 am

Just about any M series harness for a 1949 thru 1960 M series truck can be adapted to an M38 or M38A1 or M170. Just how much converting depends on which harness. All you need to make a decision is to compare the the wiring diagram of the donor to the jeep you have and note the differences in vehicle lengths and positioning of terminal ends.

circleburner12 · Post by **circleburner12** » Fri Mar 04, 2016 1:03 pm

very interesting and may consider it to keep 24volt components. shortning the ends wouldn't be a huge problem. wes what else kind of trouble would a person face if he tried a m35 or m35a2 harness on a m38?

Wes what is a rio m35 harness?

HAS anyone tried or has did this by using a m35 harness?

thxs