Several months ago I had an after market trailer wiring harness installed in my 08 XLS. I purchased the recommended kit to convert the LED system to the std trailer lights and the installer did run the power directly to the battery. He did not however tie the system into the harness located over the right rear wheel but instead appears to have run the harness somewhere into the rear lighting on the left side.
System seemed to work when first installed as verified by a trailer I was towing. Went to use the system again today and found the tail lights on the trailer not working. Brake and turn signal lights work.
I'm no electrical genius but I connected a multi meter to the ground and brown wire lead on the trailer harness.
When the car lights are turned on, I get less than 1 volt to the brown lead. With the lights turn off, I'm getting 12.3 volts to that lead. Even though there is voltage at that point the lights on the trailer are not lit, so I assume there is no current.
Like I said, I'm basically just fumbling around when I test this stuff but that result seemed very wrong. Anyone have a suggestion of what may be wrong.

 

i suggest using ONLY the factory wiring harness.

buy one and get rid of the aftermarket junk.

 

i also would like to suggest you to buy an OEM wire harness. Because you will not need to afraid of wiring it wrong. Just need to jack your car and work underhood, rear of the car and under the car just to plug them up. I don't even see any of the wires explosed. So, think about it. It just cost you around $70.

 

Could someone post the install instructions for the OEM harness?