Trailer Running Lights Not Working with Wiring Harness 118422 on a 2008 Jeep Commander

Question:

I used the t-one wiring harness on my 2008 jeep commander and have no running lights on my boat trailor although when I switch my trailor to my sonoma truck they work fine, what is my problem? I have turn signal - brake lights but no running lights on the commander.

asked by: Kevin

Expert Reply:

Since the lights on the trailer work on a different tow vehicle, we can eliminate the trailer as the problem and focus on the wiring harness and the 2008 Jeep Commander. The running light wire on the harness is the brown wire. It is on the same side as the yellow wire which should be on the driver side of the vehicle.

You can test the wiring harness using a circuit tester like # PTW2993. Do this test without the trailer connected. Turn on the running lights on the vehicle and use the circuit tester to probe the brown wire going into the harness. If there is no signal, make sure the vehicle running lights are working by disconnecting the wiring harness and plugging the taillight back into the factory connector.

If the taillights are not working on the vehicle, something is wrong with the vehicle wiring. If they are working, check the wiring harness connectors for any bent or broken pins.

If there is a signal on the brown wire leading into the converter, check the brown wire coming out. If there is no signal something is wrong with the converter, and it will need to be replaced. If there is a signal coming out, move down to the 4-Way. Test the pin for the running light circuit on the 4-Way. If there is no signal, there is a break in the wire somewhere between the connector and the converter.

If there is a signal, make sure that the pin location matches the one used on the trailer. Clean out any dirt and corrosion in the vehicle and trailer side connectors for a better connection.

You will also want to make sure the converter box white wire is grounded to a bare metal surface. Some vehicles require a relay or a fuse to allow the trailer lights to work. While this is unlikely on your vehicle, if nothing else seems to work, you can check the owner's manual for the running light fuse location to determine if it can handle the extra power draw from the trailer lights.

expert reply by: Michael H