Blowing tow/haul fuse

I've never used the 7way connector before, so when I discovered that my new trailer didnt have running lights, I checked the fuses. Blown. When I replaced it, it immediately blew again. What should I check next? Would there be a bare wire somewhere on the truck maybe?

 

Yes, it was with the trailer plugged in. The brakes and blinkers work, but no running lights (which I assume is this fuse). I applied 12 volts to the running lights on the trailer and they came on nicely, independent of the truck. So i guess i am chasing that running light wire through the trailer?

Thanks

 

Bum wire or grounding problem with the trailer? Sometime trailers can be a PITA!!!

 

So I had a trailer blowing my fuses like crazy. There was 2 frayed wires in the trailer side of the harness I didn’t see that were contacting in turns

 

I had this same issue and it was a corroded wire in the plug itself. Rewired the plug, replaced the two/tail fuse and all was well.

 

Found it. The running lights wire had a rub spot in it and it was grounding. Taped it up and viola. Now my back is not happy about my gravel driveway, lol.