Perplexing Lighting Problem

[Big Mike]

My truck...'14 3500 CC DRW, blows the clearance light fuse, only when I hook up to my fifth wheel. Here is the perplexing part, the trailer plug, has power everywhere it should, meaning all trailer lighting and brakes work after said fuse has blown. This leads me to believe the problem is not with the trailer, but something with the truck. The only lights out on the truck are the cab clearance lights, fender lights, and dot bar on the rear. parking lights still work, along with all other lights.

If I replace the fuse, and do not hook up to the trailer, the fuse does not blow, but from what I can tell, the clearance light circuit has nothing to do with the trailer light circuits? The trailer lights all still work once the fuse blows.

Does anybody have any ideas?

Thanks,

Big Mike

 

[Hoefler]

Check the routing of the wire for the rear fender clearance lights, the rear ones. On mine, the wire was between the overload and the hanger. Was fine until hooked to a trailer. My dealer replaced and re-routed the wire over the frame. The left side was blowing the fuses, the right side was the same way, just hadn't shorted out yet.

 

[sag2]

Does it blow fuse 29 or 79?

See attached wiring diagram.View attachment FUSES-RELAY---MISCELLANEOUS.pdf

 

[Big Mike]

Blows #79

Thanks,

Big Mike