Wiring help

Quarter-ton trailer series, Wanted, USED PARTS FOR SALE NO EBAY or COMMERCIAL SALES., and Knowledge Base
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TonyStandefer
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Wiring help

Post by TonyStandefer » Sun Apr 01, 2018 3:32 pm

Finishing up my bantam trailer this weekend finally got my tires mounted on the rims and the trailer is mobile again. However, when I plugged in the vehicle cable it trips the circuit breaker on the jeep. Nos vehicle cable and switch, mv spares wiring harnes. I have checked grounds and wiring on the jeep socket I plan on checking the trailer switch next, I hated wiring that trailer switch and am not happy at the thought of having to toubleshoot it, any thoughts on this?

The breaker trips as soon as I plug into the socket
Willys MB 340931. DOD 6-9-1944
Mvpa 1996 convention 1st place motorpool class
Dodge wc-12, July, 1941


Joe Gopan
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Re: Wiring help

Post by Joe Gopan » Sun Apr 01, 2018 4:31 pm

With the head and brake lights off, there should be no live wires back there. Double check the Jeep light switch wires I have no clue without being there. I was very careful wiring my MBT using a NOS GI Harness and still had issues with with the trailer lights.
2011 MVPA PIONEER AWARD - MVPA #1064
HONOR GRAD-WHEELED VEHICLE MECHANIC SCHOOL 1960 - US ARMY ORDNANCE SCHOOL(MACHINIST) ABERDEEN PG 1962 - O-1 BIRD DOG CREWCHIEF - 300,000+TROUBLE FREE M-38A1 MILES
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Chuck Lutz
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Re: Wiring help

Post by Chuck Lutz » Thu Apr 05, 2018 8:36 am

Tony....

I'm with Joel here....there should be no power to any of the terminals in the jeep trailer socket on the rear panel. If you are blowing the CB with NO lights on and NO brake pedal stepped on then there is the issue....there should be no power to the socket until you turn on the lights or step on the brakes.
Chuck Lutz

GPW 17963 4/24/42 Chester, PA. USA 20113473 (USA est./Tom W.)
Bantam T3-C 1947

TonyStandefer
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Re: Wiring help

Post by TonyStandefer » Thu Apr 05, 2018 5:23 pm

To clarify with the plug inserted into socket, then turning on lights at the switch the breaker would quickly trip. I knew I had lights at the vehicle it had to be in the trailer. I mapped the wires going to plug to make sure that the socket was wired correctly, then I checked the plug, after taking the plug apart on my nos cable I discovered two of the wire terminals were touching. Probably shorting. I repositioned the wire and made sure brake, tail and ground wires matched positions between trailer and socket. I tested again and the breaker no longer trips, I have tail but no brake light on trailer. Went back to socket and made sure brake terminal was getting juice when brake applied, it wasn't. Traced wire back to switch and found a loose wire on switch. Tightened then moved back to socket, socket now getting juice. Finally retested trailer, still no brake light. Jumped to taillight socket to test, wire had juice, repositioned in light socket and reinstalled
Bulb. Finally got it working. A long exercise in electrical testing and logically working through troubleshooting. I am glad I did not have to dig back into the trailer switch, that thing was a pain to wire!
Willys MB 340931. DOD 6-9-1944
Mvpa 1996 convention 1st place motorpool class
Dodge wc-12, July, 1941

Joe Gopan
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Re: Wiring help

Post by Joe Gopan » Thu Apr 05, 2018 6:47 pm

Using Int/Ext Tooth Lock Washers goes a long way to eliminate grounding issues. The MBT can be a challenge.
2011 MVPA PIONEER AWARD - MVPA #1064
HONOR GRAD-WHEELED VEHICLE MECHANIC SCHOOL 1960 - US ARMY ORDNANCE SCHOOL(MACHINIST) ABERDEEN PG 1962 - O-1 BIRD DOG CREWCHIEF - 300,000+TROUBLE FREE M-38A1 MILES
LIFE MEMBER AM LEGION-40/8-DAV
7 MIL SPEC MAINTAINED MV'S
COL. BRUNO BROOKS (ARMY MOTORS) IS MY HERO

TonyStandefer
Sergeant Major of the Gee
Sergeant Major of the Gee
Posts: 474
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Re: Wiring help

Post by TonyStandefer » Thu Apr 05, 2018 7:34 pm

Agreed I just went through Paolo batiste book and made sure my jeep had proper grounding with lock washer locations including between socket and body. I still have a few locations to check including some of the body bolts. I put tooth washers on the trailer ground position by the switch as well as the tail light brackets and tail light buckets. Even with all that I still had issues to troubleshoot
Willys MB 340931. DOD 6-9-1944
Mvpa 1996 convention 1st place motorpool class
Dodge wc-12, July, 1941

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Chuck Lutz
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Re: Wiring help

Post by Chuck Lutz » Fri Apr 06, 2018 9:29 am

Tony....

If you think messing around in the B/O switch is bad....think about how wiring in the harness to it for the Tandem Trailer Socket on the rear of the trailer can cause you grief! Ask me how I know! I ran another harness from switch to the Tandem Socket like this:
R Mid Wiring.jpg
R Mid Wiring.jpg (189.33 KiB) Viewed 621 times
R Rear Wiring.jpg
R Rear Wiring.jpg (165 KiB) Viewed 620 times
Socket Box Side.jpg
Socket Box Side.jpg (169.92 KiB) Viewed 621 times
Chuck Lutz

GPW 17963 4/24/42 Chester, PA. USA 20113473 (USA est./Tom W.)
Bantam T3-C 1947

Joe Gopan
Jeep Heaven
Posts: 49841
Joined: Sun Mar 02, 2008 12:37 pm
Location: Proving Ground

Re: Wiring help

Post by Joe Gopan » Fri Apr 06, 2018 9:45 am

Install 4 Int/Ext Tooth lock washers per Tail Light, or the lights can give you a hard time by not being grounded. Two washers on either side of the Trailer Tail Light bracket.
A check of your trailer parts manual will confirm the quantity and type of washers for those locations.
2011 MVPA PIONEER AWARD - MVPA #1064
HONOR GRAD-WHEELED VEHICLE MECHANIC SCHOOL 1960 - US ARMY ORDNANCE SCHOOL(MACHINIST) ABERDEEN PG 1962 - O-1 BIRD DOG CREWCHIEF - 300,000+TROUBLE FREE M-38A1 MILES
LIFE MEMBER AM LEGION-40/8-DAV
7 MIL SPEC MAINTAINED MV'S
COL. BRUNO BROOKS (ARMY MOTORS) IS MY HERO


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