M100 tail lamp issue

Quarter-ton trailer series, Wanted, USED PARTS FOR SALE NO EBAY or COMMERCIAL SALES., and Knowledge Base
Ron D
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Re: M100 tail lamp issue

Post by Ron D » Mon Jan 03, 2022 12:51 pm

There's no need to disassemble. It's fairly simple to check wiring with an ohmmeter. No power applied. Not connected to the jeep.

It would help to have a wiring diagram to use with the ohmmeter to verify it's wired correctly (maybe in the past somebody took it apart and put it back together wrong).

Pin A on one end of the cable goes to Pin A on the other end of the cable, and so on, B to B, C to C, etc.
And then the big connector on the end of the cable has to be keyed (clocked) the same with the socket on the jeep, so that Pin A mates to Pin A all the way through everything to where it belongs, B to B, etc, etc.

Not hard to do. Maybe 15 minutes time if that much.
Even if you bought a defective cable and the vendor will exchange it, at least you know how to determine if it's good or not.

Good luck!
Ron D
1951 M38
1951 M100


Rick E.
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Re: M100 tail lamp issue

Post by Rick E. » Tue Jan 11, 2022 2:37 pm

Thanks Ron. The vendor is not responding to my requests on eBay. Seems a reputable vendor but does not respond. Militarysurplusparts is the vendor. Anyone know a phone number?

As for the cable, I did test it and I got some bleed over of voltage to non-energized circuits. Thus, I thought there is a problem in the plug with some pins/wires touching partially.

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Bill H.
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Re: M100 tail lamp issue

Post by Bill H. » Tue Jan 11, 2022 6:01 pm

Rick E. wrote:
Tue Jan 11, 2022 2:37 pm
Thanks Ron. The vendor is not responding to my requests on eBay. Seems a reputable vendor but does not respond. Militarysurplusparts is the vendor. Anyone know a phone number?

As for the cable, I did test it and I got some bleed over of voltage to non-energized circuits. Thus, I thought there is a problem in the plug with some pins/wires touching partially.
I just went through this with an eBay seller over a very expensive three row radiator that failed. It was listed with an unconditional lifetime warranty. After five months and dozens of emails and messages and having eBay involved I got zero satisfaction (not one reply to any of them)! EBay could not get them to respond either! EBay said their hands were tied and I should keep attempting to contact them. When an eBay seller refuses to even respond to an issue it really sucks! The last I checked the seller is still selling on eBay! :roll:

I'm out the initial cost of the radiator, R&R labor and the radiator shops repair charge (about 3X the initial cost) and nearly two weeks down time. I hope you have far better luck!
Bill H.

"Each shall seek his own kind, in other words, a bird may love a fish but where would they build a home together?" Tevye, Fiddler on the Roof

1952 Dunbar Kapple M100
1953 Willys M38A1
1962 AMC M422A1
1965 Stevens M416B1 X 2
1967 Kaiser M715

2 Timothy 3:1-5

Rick E.
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Re: M100 tail lamp issue

Post by Rick E. » Wed Jan 12, 2022 6:35 am

Thanks Bill. I do not believe this seller even looks at emails. I sent at least two before I purchased the cable. I wanted to know the exact length. Silence. I bit the bullet and just purchased it. Now I have the issue...

Steve Webb
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Re: M100 tail lamp issue

Post by Steve Webb » Wed Jan 12, 2022 1:45 pm

If it was shipped domestic and you have an address only way probably to get things going is writing a letter.
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Marty, SoCal
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Re: M100 tail lamp issue

Post by Marty, SoCal » Mon Jan 17, 2022 1:40 pm

Make sure you have some star lock washers under the lamp and lamp mounting bracket bolts. Sure sounds like a bad ground to me. A voltmeter from the lamp housings on bare metal to the negative in the tow vehicle will show the voltage drop in the circuit. Should have less than 0.5V shown on the meter with the lamps on.
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Rick E.
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Re: M100 tail lamp issue

Post by Rick E. » Fri Feb 04, 2022 6:20 am

Marty, you are most likely correct. Nothing wrong with the trailer wiring. I replaced the intervehicular cable to no avail. Rebuilt left side tail light guts. Cleaned up grounding surfaces, perhaps not enough. Back to the drawing board.

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Re: M100 tail lamp issue

Post by Rick E. » Tue Feb 08, 2022 12:00 pm

Ground issue 100%. I cleaned all the ground surfaces from the plug socket on my m38 to the taillight housings and mounts in the rear. I was only getting about 6 volts back there. I had an epiphany one morning and kicked myself! I had taken the entire trailer apart and epoxy primered and painted it, including taking off the drawbar pieces. I cleaned up all the ground connections but that one.

So one bolt removed to access paint removal then reinstallation. Works like a charm with the exception of popping a breaker on the M38 when the headlights are on and the brakes applied. 70 year old breaker needs replacement next.

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Bill H.
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Re: M100 tail lamp issue

Post by Bill H. » Tue Feb 08, 2022 1:42 pm

That is awesome! Thanks for sharing the remedy.
Bill H.

"Each shall seek his own kind, in other words, a bird may love a fish but where would they build a home together?" Tevye, Fiddler on the Roof

1952 Dunbar Kapple M100
1953 Willys M38A1
1962 AMC M422A1
1965 Stevens M416B1 X 2
1967 Kaiser M715

2 Timothy 3:1-5


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