I have a NOS main harness I want to put in my 52 M38. The diagrams in the manual aren't to clear on which wires to to the 4 circuit breakers. I only have the regulator harness and main harness right now but wanted to get a start putting it in. Can anyone explain what wires go to the circuit breakers? My jeep was disassembled when I bought it so I have no clue as to where it was.
Thanks
Rick
PS Any opinions on using the old harness with new stuff mixed in? Should I just buy the whole kit?
Wiring my M38
Moderators: TomM, Moderator, wesk
Depending on the harness configuration (Old or New, meaning the dash breakers or the cowl battery box breakers) will determine where your harness goes...
I have the Cowl battery box breakers and the regulator harness should have a large wire with 3 double douglas connectors on it. This wire daisy chains from one breaker to another providing power to all three... then the other side of the breaker supplies the power to the proper circuit...
I hope this helps...
I have the Cowl battery box breakers and the regulator harness should have a large wire with 3 double douglas connectors on it. This wire daisy chains from one breaker to another providing power to all three... then the other side of the breaker supplies the power to the proper circuit...
I hope this helps...
- Ryan_Miller
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- Location: Kansas
Rick,
The new harness vs the older harness would mostly depend on the condition of the old harness. If it looks to be in good condition, try it out, if you have any electrical problems that you cannot trace very easily then I would be leaning toward a new harness.
On the circuit breakers:
There is only one diagram that shows all of the CB leads on the same diagram and that is the complete wiring diagram, which can get confusing. The circuit breakers are part of several different circuits so you have to look up each circuit diagram (ignition, lights, etc.).
I would buy the TM9-804 as it has all the different ciucuits laid out in about 10 different diagrams and it is not as complicated when broken down to basic circuits.
The TM9-804 is available in reprint - call Midwest Military ot one of the other suppliers.
This is the Early M38 wiring from TM9-804 September 1950
complete wiring diagram page:

page 119 ignition diagram that shows the three circuit breakers on the battery box and the instrument cluster circuit breaker. One of the not shown leads on this diagram can be traced on the previous diagram above to go to the firewall auxillary outlet.

The new harness vs the older harness would mostly depend on the condition of the old harness. If it looks to be in good condition, try it out, if you have any electrical problems that you cannot trace very easily then I would be leaning toward a new harness.
On the circuit breakers:
There is only one diagram that shows all of the CB leads on the same diagram and that is the complete wiring diagram, which can get confusing. The circuit breakers are part of several different circuits so you have to look up each circuit diagram (ignition, lights, etc.).
I would buy the TM9-804 as it has all the different ciucuits laid out in about 10 different diagrams and it is not as complicated when broken down to basic circuits.
The TM9-804 is available in reprint - call Midwest Military ot one of the other suppliers.
This is the Early M38 wiring from TM9-804 September 1950
complete wiring diagram page:

page 119 ignition diagram that shows the three circuit breakers on the battery box and the instrument cluster circuit breaker. One of the not shown leads on this diagram can be traced on the previous diagram above to go to the firewall auxillary outlet.

Ryan Miller
MVPA # 22010
MVPA # 22010
- wesk
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This is the best view:

In this diagram if you have a single plug light switch just delete the trailer plug info. With the light switch which goes single plug at MC35388 and the circuit breaker trio ends at MC65927 and the instrument CB goes away at MC65042.

In this diagram if you have a single plug light switch just delete the trailer plug info. With the light switch which goes single plug at MC35388 and the circuit breaker trio ends at MC65927 and the instrument CB goes away at MC65042.
Wes K
45 MB, 51 M38, 54 M37, 66 M101A1, 60 CJ5, 76 DJ5D, 47Bantam T3-C & 5? M100
Mjeeps photo album: http://www.willysmjeeps.com/v2/modules. ... _album.php
45 MB, 51 M38, 54 M37, 66 M101A1, 60 CJ5, 76 DJ5D, 47Bantam T3-C & 5? M100
Mjeeps photo album: http://www.willysmjeeps.com/v2/modules. ... _album.php
- RickC
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- Joined: Sun Apr 10, 2005 6:00 pm
- Location: Coventry, RI
Thanks guys. I am familiar with M series wiring. I own a M37 and M43. Harness I have doesn't really have any leads that appear to go to the battery box breakers and I didn't see where the dash breaker was fed from. The 2 jeeps I have both had dash plates with a breaker on them as well as 3 breakers on the battery box. The regulator harness is no problem as it is basically the same as the m37 ones where it feeds the battery box breakers and the ignition switch. Maybe just easier to go with a repro harness kit.
Rick C
Rick C