Troubleshooting Trailer Wiring Where All Lights Blink with Left Turn Signal

Updated 04/29/2019 | Published 04/27/2019

Question:

i connected new wiring harness to F150-HM48240 Looks like a short all lights blink when left turn signal on. Checked plug on trailer and noticed brake wire unplugged. Will this cause short when plugged into F150? When this trailer is plugged into my my 2003 ford explorer all lighting works fine no problems . what is the problem when plugged into F150? Thanks for your help!

asked by: Chris K

Expert Reply:

With your 2015 Ford F-150 it sounds like there is a bad ground on your trailer or a bad connection. First I recommend using some sand paper on your wiring connection to ensure there is good contract between the pins free of corrosion and debris.

The Hopkins Endurance 4-Way Flat Trailer Wiring Harness - 20' Long # HM48240 may be connected correctly and work well with a different vehicle that has a different power output, but often when there is an issue like you are describing it's a ground issue. I recommend disconnecting your current ground then using some sand paper to get a bare metal to metal connection between your ground and the trailer frame. Next check your tail light ground connections which if not on a separate wire, will ground through the mounting hardware. Make sure those connections are also bare metal to metal. Once you have done this with every light, you can plug it back into your F-150 and that should solve your issue. If not, let me know and we can continue to troubleshoot.

expert reply by: Jason S