No Stop or Turn Signal Lights On Trailer When Using 4 to 7-Way Adapter

Question:

I purchased a 7 blade to 4 flat adapter. when I connect them I get the running light to work on the trailer but no signals or brake lights. ive looked at the wiring harness for the 7 blade on my vehicle and it seems fine. the adapter worked on a friend of mines truck. what am I missing? thank you

asked by: Jonathan B

Expert Reply:

It sounds like you have an issue with the turn/brake signal circuit on either the vehicle or trailer. I recommend you first test this circuit on the vehicle side trailer connector. If you don't get power here then you most likely have a blown fuse or loose wire.

If you do get power on the turn/brake signal circuit then apply a 12 volt hot lead to the trailer side trailer connector on the turn/brake signal circuit. Once this is done start testing the wire with a test light while working your way back to see where the power stops.

If you are not able to get any power on the trailer side trailer connector with hot lead attached then the issue is with the trailer ground.

expert reply by: Conner L