Troubleshooting Trailer Running Lights Staying On when Vehicle is Turned Off

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Question:

my trailer parking lights stay on when the vehicle switch is off

asked by: david p

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Expert Reply:

It sounds as though there is a short or something is mis-wired. Using a circuit tester, like the # PTW2993, check the connection points in the vehicle side connector, to see if there is constant power on the running light circuit (brown wire on the 4-Way) when the vehicle and lights are turned off.

There should be no signal when the lights are off, and a signal when they are on. If there is a signal with the lights off, then there is a problem on the vehicle side. Check to make sure that the brown wire is properly connected to the running light wire at the rear of the vehicle and that the white ground wire is attached to a bare metal surface that is free of dirt and corrosion. It could also be a bad converter.

To test a converter, you will need to first test the wiring going in for function. If the functions are incorrect going in, then something is mis-wired and you will need to start again as if installing the unit for the first time. I have included a link to the installation details for the # C59496 below for reference. Depending on the vehicle, you may need to pay special attention to the directions regarding 2 wire and 3 wire systems and install according to the wiring on your vehicle.

If the functions are correct going in to the converter but incorrect going out, then there is a problem inside the converter and it will need to be replaced. If the signals are correct going in and coming out, the issue lies elsewhere. I have included a video below, on testing a converter, that should help.

If there is no signal with the lights off, then the issue is on the trailer side. If your trailer has a separate battery, make sure it is not connected to the tail light wiring. Also check to make sure all of the grounds are secure and attached to bare metal surfaces free of dirt and corrosion.

You should also check all of the ground connection points on the trailer to be sure the power is not back feeding through the ground when the vehicle is turned off and the trailer is connected. The power from the 12 volt connection could be looking for a ground and is finding the connection through the taillights. Check the taillight connections to the trailer and the ground at the trailer coupler to be sure they are connected to good clean trailer frame grounds.

expert reply by: Michael H

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Answer 1

I suspect your problem is caused by a damaged or corroded trailer connector. Take a look at your trailer connectors, both the socket on your truck as well as the plug on the trailer. Look for green or white corrosion on the pins or sockets of the…

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Answer 2

This sounds like the problem could be a short or possibly ground related but based on what you have said a ground is much less likely. Look for any pinched or frayed wires on the trailer and fix as needed. This could cause a short resulting in…

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Answer 3

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…

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Answer 4

We know from Tekonsha training on their universal-fit ZCI Circuit Protected Vehicle Wiring Harness #119250KIT that this item is very sensitive to the initial setup process, which must be followed exactly for correct operation. My technical contact at…

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Answer 5

This can occur with some Curt wiring harnesses. On a trailer with LED lights the lights may be dimly lit when the vehicle is off because the harness has a direct connection to the battery and there is some power to the 4-Way all the time. If the…

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Answer 6

The most likely scenario that would lead to your right tail light staying on even after it is unplugged is that somewhere along the wires running through your trailer, there is an inadvertent bare connection between your right tail light wire and the…

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Answer 7

If you can tell me the year, make, and model of your tow vehicle I can then look up what the code is referring to but if not you can find this info in your owner's manual. If the left brake light stays on all the time even with the trailer…

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Answer 8

Generally you see this situation on a vehicle that has LED lights because there is a power bleed coming from a different circuit into the lighting circuit. LED lights require a lot less power than incandescents, that's one of the biggest benefits…

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Answer 9

Typically when a trailer function stays on after the vehicle has turned of the problem is a fried aftermarket 4-way converter box. Or, if the lights are LEDs sometimes you will see the lights dimly lit. If you have an aftermarket 4-way converter box…

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Answer 10

There are quite a few differences. The ones you can see easily on the outside are the display and control buttons. The P3, part #90195, uses a multi-color LCD to provide more information where as the Primis IQ uses basic LED numbers like what you…

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Answer 11

There should be five wires on your trailer side connector, a white wire which is for a ground, the yellow/brown and green/brown are for the running lights, a green wire for the right turn/stop light, and a yellow wire for the left turn/stop light…

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Answer 12

Hey Kris, thanks for reaching out! You'll already have a good idea of how to adjust the Tekonsha Prodigy P3 #90195, but it would be good to do a bit of a test run once your trailer is loaded just to make sure the brakes are operating safely and…

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Troubleshooting Trailer Running Lights Staying On when Vehicle is Turned Off

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