Troubleshooting Voltage Drop When Trailer Running Light Circuit is Connected

Updated 08/31/2021 | Published 08/30/2021

Question:

All lights are working except the running lights. When I check voltage on the green wire in the junction box coming from the truck I have 12.5 volts as long as it’s disconnected from the green wire and yellow/white wire coming from camper side. When I put the 3 together the voltage s to a low erratic reading .04 -.8. I think I have a grounding issue? Surprisingly it does not blow a fuse anywhere. When I disconnect the wires the green supply goes right back up to 12.5 volts.

asked by: Jonathan M

Helpful Expert Reply:

The running light circuit of your trailer wiring is definitely shorting to ground which is causing the problem you are having. You'd need to go over the wiring of that circuit and fix any cut or exposed wire as needed.

expert reply by: Jameson C