How to Determine Which Fuse on Vehicle to Check for Trailer Wiring

Published 10/09/2019

Question:

I accidentally caused short on trailer I need to know what fuse blew in vehicle

asked by: George N

Expert Reply:

It all depends on what circuit isn't operating anymore for your trailer. For basic 4-Way wiring you have the running/tail lights, the left turn/stop, and then the right turn/stop. If you have a 7-Way then it could be any of those or you also have the possibility of the reverse light function, brake controller output, or 12V power. I am attaching some photos showing where the various pins and their functions would be located as well as some troubleshooting articles on wiring.

If you aren't sure what fuse blew you can use a circuit tester like part # PTW2992 to test the different pins on your vehicle connector and compare them with the pins in the diagrams I attached. You can then look in your owner's manual under "fuses" and it will let you know what fuses are for which functions.

Please note that you need to make sure that you have the problem fixed that caused the short because if you don't your fuse will just blow again.

expert reply by: Jon G