Trailer Receptacle

Boze · Post by **Boze** » Thu Aug 19, 2010 2:04 pm

I have a bit of a problem with my trailer receptacle. I have an M38 with a new wiring harness from Vintage Wiring. I found the trailer side plug of the connection to the M100/M416 trailer harness at a flea market. The connector was cut off with about 4" of cable. I plugged it into the Jeep harness and used Wes' pin drawing to find the correct wires for service tail and service stop lights. Since my trailer is a civilian, I am using a standard 4 wire civilian harness, lamps and LED bulbs. (L, R, T and G) However, when I connect the civilian harness (which works OK with my car) to the appropriate wires on the connector, the lights to not light up. Instead, the lights only work when I turn the multi-function light switch to BO marker and BO stop. When in the service light mode, none of the trailer circuits will energize. Is my harness bad? Or is my connector a different one that may be the wrong one for an M38? Or, am I going insane? My Jeep lights work perfectly according to switch position.

Post by **wesk** » Thu Aug 19, 2010 9:25 pm

Boze,

I am not sure which diagram you are using.

This is the standard military trailer receptacle wiring and pin-out.
Some pins are not used with the M38. Also be sure you have the correct pin for wire 90 to ground the trailer to the jeep.

This is the set-up I use for adapting the military receptacle to a civilian trailer harness. Remember you must use 24 volt bulbs in your civvy trailer when doing this. I usually wire the ground in a "Y" to pickup both pins D & L so no matter which MV's receptacle I connect to I will catch the wire #90 ground.

Boze · Post by **Boze** » Sun Aug 22, 2010 3:33 pm

I have been using the top diagram. The problem seems to be that the circuits on the trailer receptacle do not seem to match the diagram. As I said in my first post, the service stop and service tail do not light up with my 24v tester through the receptacle. I do get some to light up but they are on the BO tail and BO stop circuits. It would appear that somehow the wires (or tags) became crossed at the factory. The Jeep lights all work, but the receptacle does not work in the same way.

The Jeep and trailer are stored off site and work prevents me from getting back to them for a week or so. I see in the diagram that it shows Packard connectors in the lines feeding the receptacle. I did not see these in my Jeep - perhaps they are tucked behind something. Or maybe there are not there?

If the receptacle and trailer plugs are standard and no variance should exist, I think I will have to stab the wires leading to the receptacle with my tester to verify which wire is on which circuit, and relocate the correct circuit wire to the proper lead going into the back side of the receptacle. As far as grounds, I use a dedicated ground wire for each lamp on the trailer and continuity has been verified. BTW: I use LED bulbs which are rated for 6-30vdc, so I can pull the trailer behind my car (12v) or my Jeep. (24v) These were recommended to me by a dealer at Topeka.

Cacti_Ken · Post by **Cacti_Ken** » Sun Aug 22, 2010 9:37 pm

Did you install the wiring harness and trailer receptacle? Or did someone else? sounds like some wires got connected wrong.

Boze · Post by **Boze** » Mon Aug 23, 2010 12:45 pm

I bought the harness from one of the major dealers, who had it made by the only company know that makes them. I installed it myself but this was 5-6 years ago.

When I get a chance to crawl under it again I will look for Douglass (not Packard) connectors to see if they are connected properly per the spec. Otherwise, I think I will have to stab, verify, cut and splice. Or - change the aluminum tags so they match and reflect what the circuit really is? Maybe this was just an "Oops" occurrence at the factory and the tags were incorrectly applied.

SAFEHOME · Post by **SAFEHOME** » Sun Oct 17, 2010 2:56 am

I have a similar problem that recently developed with my (1952 M100) trailer lights. Apparently there are some shorts in the (original) cable that plugs into the back of the jeep (1952 M38-A1). I suspect that the problem is in the jeep end of the cable since that has been hanging upside down out in the rain for years. My question is: HOW DO I DISASSEMBLE THE PLUG WITHOUT DESTROYING THE RUBBER PARTS? Thanks in advance.

Post by **wesk** » Sun Oct 17, 2010 10:15 am

The manual that covers that is the TM 9-1825E Bendix-Scintilla component service manual.

You can download the applicable pages at my photo storage site:
http://tm9-1825e.mypicgallery.com

SAFEHOME · Post by **SAFEHOME** » Mon Oct 18, 2010 12:58 am

Thank you.

SAFEHOME · Post by **SAFEHOME** » Mon Oct 18, 2010 3:09 am

Wes. Although I'm pretty good with the computer, I can't get a decent read on the pages of TM 9-1825E that interest me (pps 102, 103 & 104) because the image loses too much definition as I enlarge it. Any chance of getting a pdf or other format file of those pages or a quick workaround? Thanks again. dwm

Beacher425 · Post by **Beacher425** » Mon Oct 18, 2010 7:34 am

Me, too. I would greatly appreciate the affore mentioned pages in pdf.
Thanks in advance if it is possible,
Jeff

Post by **wesk** » Mon Oct 18, 2010 9:16 am

You guys must be downloading the medium size image. You need to click on the thumbnail you want and then click on the medium photo and the large will appear in a new small window.

Here's the large page 102 off my photo site:

SAFEHOME · Post by **SAFEHOME** » Mon Oct 18, 2010 9:57 am

Wes, AS USUAL, you're right on. DUH !! How I missed it, I don't know. Now I have downloaded and printed the entire (excerpted) manual. Thanks again. dwm

Post by **wesk** » Mon Oct 18, 2010 11:23 am

You are welcome. Oddly enough this manual is virtually non-existant here in the US. I gained my original paper copy from a European Museum.

SAFEHOME · Post by **SAFEHOME** » Mon Oct 18, 2010 11:47 am

Wes, I know I'm pushing it a bit, but ... would you happen to have page 105 et seq.? That's where they really get into the quick-disconnect conector, which is what I have. By the way, my "plug body" has a quick hose clamp on the small end (near where the cable exits). I haven't seen it pictured in the TM yet. The thanks continue. dwm
Here in Italy there is a lot of MV enthusiasm. Nearby is an active group dedicated to studying and re-enacting the Gothic Line campaign. Lot's of history right nearby.

Post by **wesk** » Mon Oct 18, 2010 1:12 pm

I got 105 thru 111 up. I'll have to finish later on 111 thru 122