No Power To Running Light Pin On Vehicle Trailer Connector

Updated 07/23/2024 | Published 06/11/2019

Question:

I have brake and turn signal lights but tester shows no power to plug for tail, lights. Truck tail lights work. Found one 20 amp square type plastic fuse no good, switched places with a good one still nothing. Help

asked by: Neal

Expert Reply:

It sounds like you are having an issue with the running lights on your trailer. If that is the case then since you have tested the trailer connector and found that power is not reaching this, you either have a blown fuse, bad converter, or shorted wire. I didn't catch what vehicle you have nor what trailer wring harness you are using but if it is a factory harness then most likely you just have a blown fuse. I know you said you checked the fuse but the vehicle's tail lights and trailer's tail lights are not on the same circuit so they will have a different fuse. I recommend your look in your owner's manual for the proper fuse location.

If you have an aftermarket wiring harness then most likely the converter box is bad. In order to confirm this you can test the running light wire leading into this and see if power leave this. If not then you know the converter box is bad but if nothing enters it then you know you have a wire short.

expert reply by: Conner L

Thanks F.

7/23/2024

I have a 2005 F150 four pin. I don’t see any fuses marked running lights for trailer. I have brake lights. I have directional but no running lights.

Jameson C.

7/23/2024

@ThanksF Most of the time this problem is just dirt or corrosion on the pins of the 4-way which can easily be cleaned off with sandpaper. Have you tried/checked that?