Keep Blowing A Fuse

[heavydutyfd]

Why would my father in law’s 4’x8’, 4 pin utility trailer keep blowing my (number 15 trailer running lights) 20 amp fuse? My 6’x16’, 7 pin trailer never has blown a fuse. I thought maybe the 4’x8’ was not grounded properly, so I re-grounded it, still it blew my fuse. So I re-wired the entire trailer…guess what… blew the fuse. Now here is the weird part…I went to TSC and bought a 4 pin/7 pin adaptor, and had NO problem with the fuse blowing. I have a fire and ice rear LED light bar hooked to my 4 pin darn near 24/7/365, and I have no problem with it blowing fuses.



My father in-law’s truck is a Turd F150 and does not have this problem.



I have tested the 4 pin running light wire and there is power to it, but when I hook up the 4’x8’ trailer and test it, no power…blown fuse.



Thank god I shave my head, because I would be pulling my hair out by now.



Anyone have any ideas?

 

[Matt400]

Do you disconnect the light bar when you use the trailer or is the light bar spliced into your 4 pin harness?

If you are using the light bar at the same time it may be possible that the trailer lamps in addition to the light bar are over powering your fuse. There may be something not right with your light bar and its just not showing up untill the trailer is connected.

Check this post:

PlasmaGlow Fire and Ice led light bar - DodgeForum.com

 

[heavydutyfd]

No it is not spliced, it is disconnected everytime. .

 

[Matt400]

Only thing that comes to mind at the moment then is the running light ckt in your 4 pin connector. Possibly some broken strands in the wire somewhere or the socket itself. Increased resistance + the load of the trailer lights.



You could splice in a jumper from the back of your 7 pin running light wire over to your 4 pin running light wire and see what happens. If it works good then I would just leave the jumper, if it still blows the fuse then the socket end may be bad.

 

[snuff]

how much does the LED pull in amps, i agree with the increases in resistance in the pin assem on your truck, try the jumper or replace the truck end.

 

[WILLD420]

had a wire rub in two going through the trailer frame once. Same thing. Only happened on bumpy roads.

I finally put a 10 amp fuse in the line between the truck and trailer because the old trailer keeps rubbing holes in the wiring, or it cracks and shorts out. Trailer is old, but I only use it occasionally, so I just fix it when needed.

 

[Road Dog]

The trailer still has a short. I'd start with removing all the lamps from the trailer and measuring the resistance. It should be infinite with all combinations. if that's ok then plug in the trailer and start adding lamps until it pops again.