What To Check When Trailer Lights Are Not Working After Connecting To A 2014 Jeep Grand Cherokee

Published 10/26/2021

Products Featured in This Question

T-One Vehicle Wiring Harness with 4-Pole Flat Trailer Connector

(201)

$34.94

T-One Vehicle Wiring Harness with 4-Pole Flat Trailer Connector

(346)

$78.37

Adapter 4-Pole to 7-Pole and 4-Pole

(660)

$61.81

Question:

Trailer light don’t work test all tabs at hitch and I have power and negative but not back left right brake reverse tested 4 pin and 7 pin hook ups.

asked by: Stephen

Expert Reply:

If you are getting power to everything on the vehicle side, you will need to check a few things on the trailer. First and foremost will be the grounds. This should be done for every light and if they are LED lights, each should have its own designated ground connection that is not stacked with other grounds. This is a fairly common practice, but can cause some issues and it is better for each ground to have its own connection.

Next you will need to check the wires coming out of the 7 Way plug that attaches to your vehicle. If one of more of these has shorted or broken over time, it can definitely cause the issue you are seeing. If these are good, test the wires going into the lights. If you have power, the lights will have gone bad, If you do not have power to the lights, you have a break somewhere down the line and you will need to find this and repair it.

If I completely misread this on the other hand and you do not have power at the 7 Way or 4 Way for the lights, it could be one or two other things. First, check you grounds again. I know this is repetitive and probably the first thing you did, but a bad ground is the most common issue with wiring issues.

Once the ground is checked and or repaired, you will need to check your towing fuses if you have a factory 7 Way installed, or the wires coming out of the converter box if you have an aftermarket set up. If there is no power coming out of the converter box, you will need to replace it with the Tekonsha # 118727 and then retest. If this gets everything working again, you are good to go. If it does not, you will need to replace the 7 Way with something like the Hopkins # 37185.

If you have the factory set up and either replacing the fuses or none of the fuses are blown, odds are you have a break or short in your wiring somewhere and it will be best to have either a Jeep dealer or a trusted auto shop diagnose the issue and recommend a fix.

expert reply by: Lazer S