Trailer Wiring Problem

[au_billy]

Need some help… recently purchased a 2018 Wrangler JL. I added a hitch receiver and 4 wire trailer adapter harness for electrical. I’m having trouble with the trailer wire. The running lights work fine, but neither the brake or blinker works. Interestingly, they work fine when the engine is OFF. As soon as the Jeep is cranked, they stop. Any thoughts or help is appreciated.

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[Left Field]

First thing I'd check is that the white wire is grounded properly on both the Jeep and on the trailer and no crushed or broken wire on either.

Second, a question: Does your JL have LED lighting? If so, the lamp monitoring on the Jeep may not like the extra current draw from the trailer lights. Not exactly sure how the vehicle would respond to that however but it is a possibility.

LF

 

[Husky Man]

Yep, inadequate ground is probably the most common culprit in trailer wiring problems, and can cause all kinds of unusual issues.

Whenever you have a trailer wiring problem, eliminate grounding, and go from there

Doug

 

[au_billy]

Yep, inadequate ground is probably the most common culprit in trailer wiring problems, and can cause all kinds of unusual issues.

Whenever you have a trailer wiring problem, eliminate grounding, and go from there

Doug

as far as I can tell, my ground is good. I sanded an area behind the drivers side taillight to bare metal. Is there a way I can check the ground just to eliminate a faulty harness?

 

[20-Willys]

You could use a meter to check the cables ground connection to the chassis. You can put the meter on continuity and make sure you have low resistance.

My first trailer controller actually failed and started doing goofy things like leaving the trailer lights on when the vehicle was off.

 

[Husky Man]

as far as I can tell, my ground is good. I sanded an area behind the drivers side taillight to bare metal. Is there a way I can check the ground just to eliminate a faulty harness?

Was it on the trailer that you sanded a spot to bare metal?

Does the wiring harness have a dedicated ground circuit?

Some wiring systems ground through the hitch ball, which is an extremely unreliable ground source


Doug

 

[au_billy]

I also had to run a wire to the positive battery terminal. I’ll check the connectors.

 

[au_billy]

Was it on the trailer that you sanded a spot to bare metal?

Does the wiring harness have a dedicated ground circuit?

Some wiring systems ground through the hitch ball, which is an extremely unreliable ground source


Doug

The ground is on the vehicle side. And it does have a dedicated ground circuit.

 

[garyji]

Are you trying everything "on the ball" and "off the jack"??

G.

 

[Left Field]

If you have another vehicle and/or another trailer that can be helpful too, swapping them and see whether the problem is with the vehicle or the trailer.
LF

 

[Sladester2]

Ever figure out the fix? I have the exact same issue.

 

[Heimkehr]

Ever figure out the fix? I have the exact same issue.

The OP, @au_billy might be one of the noobs who joins just to ask a Q, and then never follows up. He's tagged so that he has a chance to redeem himself.

 

[au_billy]

Not sure what this is about! I had a legit question. I still haven’t figured it out, but I also haven’t reordered the harness to give it another try. I’m still open to suggestions. Have a great day!

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