Willys bantam trailer tail light wiring problems

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Willys bantam trailer tail light wiring problems

Post by Country361 » Thu Jan 27, 2022 9:08 pm

Ok, as usual, I’m about as frustrated as I can possibly imagine. I have a 1942 Willys Bantam trailer and I have completed the restoration except for the wiring for the running and brake lights. The trailer had non traditional wiring when I bought it, along with after market tail lights. I went back to round tail lights but they’re NOT the appropriate lights with the blackout lights like should be on there to match the Jeep. They’re 12 volt like my Jeep is, just standard running and brake lights. The bulbs work on both running and brakes on, but I cannot get these wired correctly to work. I can get the running lights to work and actually managed to get one of the lights to work when the brake pedal is pushed but now it doesn’t. I made sure I have good grounds but I am wondering if the wiring harness just isn’t made to run normal 12 volt lights when braking on both left/right sides.

I have the standard wiring harness on the Jeep so I have the green wire, red wire and the black ground wire. I am wondering if this will prohibit me from installing anything other than the traditional 4 prong plug. I don’t want to do that if I can avoid it. If not, I will just order all the original parts of you guys tell me that is my only option.

Thanks for your time

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Re: Willys bantam trailer tail light wiring problems

Post by Scrumps » Fri Jan 28, 2022 4:38 am


I assume you have access to a test meter.

The first thing I would do is connect the four way plug to the Jeep, connect the black ground wire on the trailer to a good clean ground on the chassis and check continuity between the trailer and Jeep.

Then check the grounds between each light enclosure and the chassis, especially if you have bolted on light brackets.

For the tail and brake lights all you need to do is connect the trailer end of each wire (tail & brake) into a three way junction on the chassis- there are holes to thread the wires, my junctions are on the crossmember just behind the wheels. From each three way you need to take a wire to each light assembly - one to each tail light, one to each brake. With the Jeep lights switched on, you should get 12v between the tail light connection and the light enclosure. If you do, fit the lamp and you should have tail lights.

“With the aid of an assistant”, get them to press the brake pedal with the meter between the brake connection and chassis and you should get 12v. If you do, fit the light assembly and you should be good to go.

Fitting the three way allows you to have an intermediate point to check if there is a problem. It’s called the 1/2 split method.

I can’t show you my wiring as I have made my own loom to allow me to have blackout tails, normal tails and twin stop lights with the correct trailer switch - which is far more complicated than your simple need.

I hope this helps.

Dec '42 Willys MB
Aug ‘44 Willys MB
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