Joined: May 30, 2014 Posts: 3471 Location: Texas Hill Country
Posted: Tue Jan 13, 2015 4:04 pm Post subject: M37 harness vs. M38 w/turn signals
Hello Wes, et al.,
First, do not use anything in this post to wire your M38.
It relates mainly to adapting a surplus M37 harness that
has incorrect pin information for an M38.
I am getting ready to repair some basic wiring on my M38. The stuff on it currently is done with single 14 gauge store wire and three wire extension cord stuff. I am somewhat afraid of a fire at any moment. The jeep is currently 12 volts, with a three wire alternator, voltage regulator, and toggle switches for both the ignition and lights, and a dash mounted push button for start to the solenoid.
I will be using your "test harness" as a guide for some rudimentary wiring, will try and follow the M wire identification, and plan on starting with the 3 terminal M series ignition switch I have. I believe I have the pinouts. #11 is power in, #12 is power to the coil, #27 is instrument power, and #85 is accessory. Thought of using it for start switch power for now.
First. There is one #4 cable from the battery plus to the solenoid. All other power is coming off additional loop terminals on the plus side of the battery. It appears that every wiring diagram I've seen shows just the solenoid feed from the battery to the solenoid on 12 volt jeeps. All other power comes off the same solenoid post on the solenoid, i.e., wire #10. Is this correct? If so, I will fix this issue first by removing everything south of the solenoid and replace with one 14 gauge wire (#10) to fuse or circuit breakers, then on to pin #11 on the switch.
Second. We both bought those M37 (sic) wiring harnesses for which you were kind enough to provide a detailed wiring diagram. Again I am looking at a basic harness and plan on using an extra trailer wiring harness I bought for material for the rear jeep wiring as well as the work above. In looking at the M-38 early and late as well as turn signal wiring diagrams a couple of the wire terminations at the rear of the jeep on these do not match the diagram you sent me. I have not decided on what turn signal kit yet, but shouldn't the wire terminals be the same regardless?
The reason I ask is the trailer wiring harness I have is for a big trailer, so provides a lot of extra wire, clearance light wiring, has Douglas connectors as well as the 12 pin male trailer plug. At over 30 feet, I can cut the harness some point forward of the rear light connections and splice into the M37 harness at the current 8 pin plug. I can use the excess for additional wire requirements. I would like to go ahead and put that spliced section in and wire for the right BO stop as well as turn signals, and am having trouble matching up all of the wire numbers.
Here are the pinouts on the male trailer receptacle plug:
A= 24A
B= 22
C= 24B
D= 90 ground
E= 21/489
F= 23
H= 490
J= not used
K= not used
L= not used
M= not used
N= not used
I realize this is a long drawn out query. Please let me know if you can help or what additional information I need to provide so you can.
Joined: May 30, 2014 Posts: 3471 Location: Texas Hill Country
Posted: Wed Jan 14, 2015 2:22 pm Post subject:
After a few more hours of poring over harness and connector pinouts, as well as turn signal wiring, I think I have reduced my question #2 to the following:
I am using the early Bendix Scintilla two-plug light switch. The pinouts are in the manual as well as in Wes' photo pages. The wire harness I purchased (M35 or M37 can't remember which) has the same 12 pin connector from the light switch into the harness.
Several of the pinouts for the two do not match.
I need some advice on how to adapt this harness with the early light switch I have.
I was able to figure out what wires I need to add to the trailer harness for turn signals and the right BO stop lamp.
Brian, You should delete your modification of my original early light switch pinout or make it clear that the added plug you put in the photo is incorrect and should NOT be used for wiring system work. Seems msdain used your illustration and the error in the plug's pins gave him issues on his project. _________________ Wes K
45 MB, 51 M38, 54 M37, 66 M101A1, 60 CJ5, 76 DJ5D, 47Bantam T3-C & 5? M100
Joined: May 30, 2014 Posts: 3471 Location: Texas Hill Country
Posted: Wed Jul 11, 2018 6:24 am Post subject:
Geez, I’m really sorry guys. I thought I mentioned
in my post that it related to the surplus harness I
bought for which the pins did not match the M38.
I did not know of any other way to show it than a side
by side comparison.
I have added a comment at the top of the post to that effect.
You can remove the photo from your album and annotate the photo itself to show the plug on the left is an incorrectly wired plug and then reload the photo to your album and repost the link in this post.
NEVER MIND. I DID IT FOR YOU. _________________ Wes K
45 MB, 51 M38, 54 M37, 66 M101A1, 60 CJ5, 76 DJ5D, 47Bantam T3-C & 5? M100
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