Troubleshooting Right Tail Light on Trailer that Stays On with Vehicle Ignition Off

Question

Question:

Right trailor lights stay on when i turn off ignition of truck

asked by: Randy M

0

Expert Reply:

When a trailer's tail light remains on when the vehicle is shut off, this usually indicates some kind of short in the wiring.

I first recommend using a circuit tester like # PTW2993 to check the vehicle side connector. You will want to see if there is constant power coming from the tail light circuit on the connector (brown wire). While there, also check for any corrosion or debris inside both the vehicle and trailer side connector and simply clean out as needed.

If you are in fact receiving a signal with the lights off in the vehicle, this indicates that the issue is on the vehicle side. Check to make sure that the brown wire is securely connected to the running light wire at the rear of the vehicle. Also make sure the ground (white) wire is connected to a clean bare metal surface.

If everything checks out fine on the vehicle side and you do not receive power at the connector with the vehicle off, then the issue is most likely on the trailer side. Check to make sure all of the grounds are secure and attached to bare metal surfaces free of dirt and corrosion.

If you are unable to resolve the issue, please let me know and I will be happy to look into this further. I have also attached a troubleshooting article that you might find helpful.

expert reply by: Chris R

0

Jimf

4/11/2024

Regarding: “Right trailer light stays on when I turn off ignition of truck”… My issue is similar - with the difference being that the right tail/running light on the trailer stays on all of the time: when connected to the truck, when not connected to the truck, when the trailer is plugged into a residential (120v) outlet, when the trailer is running off the (12v) battery, etc. If I disconnect the battery & residential outlet, it shuts off. I’ve inspected all wiring (which looks very good - the trailer is only 3 years old) with the exception of the actual plug - because it is molded directly to the wiring (doh !!!). I’m suspecting the issue might be with that - but checking for your thoughts…

Chris R.

4/11/2024

@Jimf You'll just have to wait for the bulb to burn out. Kidding. This is an interesting one. You mentioned inspecting the wiring, which is in good shape, but have you actually traced the wiring from that right tail light all the way to its termination at the front of the trailer? I feel like it has to be exposed somewhere and touching either a power wire that's hooked up to your battery or somewhere else. Let me know what you find or if you already did this.

Jomf

4/11/2024

@ChrisR Hi Chris, Thank you for your quick response… Actually - I inspected as much as I could (about 25%). The problem is - I can’t inspect the rest because it has a completely sealed underbelly for cold weather camping. It does have a junction block where the 7 way plug connects to the rest of the trailer wiring. Although it would be somewhat difficult/painful - I was thinking of disconnecting it at that point to isolate whether it was before or after the junction block…

Art L.

9/16/2024

@Jomf I have the exact problem with my brand new Grand Design trailer. We’re you able to resolve this?

See All (4) Replies to Jimf ∨

John R.

8/15/2024

I am having the same problem however I am verified it’s on the truck side I have been tracing wires until no resolve on is there more than one spot between the fuse panel and the engine compartment and the rear plug above the spare tire that is connected to each other that could possibly be or shorting out

Kenny H.

11/12/2024

I have a 2024 GMC Sierra HD 3500 ultimate and the right passenger side trailer light stays on even after ignition is off and I unplug the trailer lights from the seven pin connector inside the bed of the truck and tested depends on the plug and have a constant 12 volt current coming to the green wire which is for the passenger side trailer light what could it be causing this issue is it the trailer lamp control module underneath the bed above the spare tire or what I checked all fuses all relays everything and every fuse box on this truck they're all good besides one inline fuse underneath the bed at the bumper at the back there's an inline fuse that seems to be a black and white wire the black wire has the inline fuse it goes out to trailer brake wires and when I put fuse back into the slot it pops pretty soon after will not stay in without popping but that's the only issue I found at all but I don't think it has to do it with my problem with the trailer lights because that light on the passenger side stays on so therefore the right blinker does not work or brake light so break and blinker for the passenger on the trailer does not work like it's supposed to know running no just constantly illuminated very bright

Raymond M.

8/2/2025

Chris, I have a 2017 Silverado I have owned it since it was new. Prior to this year I never had an issue with the trailer lights. This year the right trailer light stays on all the time. Even with the truck turned off and key out of the ignition. When the trailer battery circuit 30 Amp. fuse is removed the problem goes away. Do you have any idea why the Trailer Battery circuit would feed the Rt. Tail Light. Ray Montana

Chris R.

8/4/2025

@RaymondM That's a good question! The Trailer Battery circuit is what would be feeding the 12V pin on the 7-Way, so my guess is somewhere down the line there's a short between that and the right trailer light circuit, possibly a bare wire making contact with the other. Another (easier) thing to check is just the 7-Way itself to see if maybe there is some debris or corrosion built up that could be bridging those two pins/circuits together, and just try and clean it out if you see anything.

Ray M.

8/8/2025

@RaymondM Chris, There was a short in the trucks bumper socket. A brushing with a wire brush fixed the short.

Chris R.

8/10/2025

@RayM Woohoo! I'm here if anything else comes up.

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Troubleshooting Right Tail Light on Trailer that Stays On with Vehicle Ignition Off

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