Troubleshooting Trailer Running Lights Circuit of Vehicle Fuse Blowing with Ground Continuity

Published 10/17/2019

Question:

I have a 2017 enclosed trailer 7-way plug that was blowing the running light fuse. I found conductivity to ground from the running light pin on the connector. I couldn’t find any bare wires, but changed the license plate bulb side marker light style,the only non led light on the trailer and that eliminated the ground issue. Could a bad bulb really have caused this issue? Thanks,

asked by: Steve J

Helpful Expert Reply:

Finding continuity to ground on the running light circuit of your trailer indicates that the circuit has a short to the frame of the trailer most likely and is your problem. What you'll need to do is trace the circuit starting at the assemblies or connector and look for a short between the wire and the frame of the trailer. This is a very common problem and the solution is finding where the exposed wire is that's touching the trailer frame and fixing as needed.

I also attached a help article on troubleshooting trailer wiring for you to check out as well for more info.

expert reply by: Jameson C

Steve J.

10/17/2019

Jameson C.

10/17/2019

While not super common what you described is possible and it sounds like you have it taken care of. More expensive light bulbs have fuses built into them that prevents the light bulb short from transferring to the power circuit of the bulb but a cheaper bulb would not have this feature which is why your blown bulb was causing the circuit to pop fuses.