Blowing fuses on tow vehicle?

[dyurisich]

Hello to all, new to forum. Having a problem with my 99 Ford Explorer blowing the trailer running lamp 15amp fuse. All turn, brake, and hazard flashers work on trailer and truck, but when I turn on the lights on the truck, it pops the fuse for the trailer. Thinking I might have a short in the plug in wire harness thats under the truck. Its a flat 4 thats been on the truck for 3-4 years. Going to replace that harness. All trailer lights properly grounded to frame, not through hitch and ball. Anyone have any different thoughts on this? I hate trailer lights and all the problems they create.

 

[huntinfool]

I personally have never had a plug go bad. I have, however, had several bulbs go bad that would short out the system and/or have some wiring on the trailer that was grounded out and cause the same problem. Switch out the plug and see if that fixes it, but I don't think that is the problem. I have had some plugs on vehicles for 20 years now and they still work fine.

My bet is that if you follow the brown wire on your trailer (this is the running lights wire) that somewhere along the wire there will be a worn spot where it is grounding out on the frame. Let us know what happens after the plug swap.

 

[Loggerhead Mike]

My bet is that if you follow the brown wire on your trailer (this is the running lights wire) that somewhere along the wire there will be a worn spot where it is grounding out on the frame.

ditto. make sure to pull the covers off your lights and inspect them good. i re-wired a trailer the other day for a feller and had part of a tail light socket broken and shorting to ground

 

[Bubba]

My brother had an issue with his lights when he bought his new 08' Triton at the beginning of this year. He was having the same issue you are having, trailer lights not working properly due to fuses blowing. He finally took it back to the dealer. Turned out when they were finishing welding up the trailer, the wire got against the metal or had a spark hit it causing a bare spot in the wire. They found the spot, replaced the section of wire and all is well.

 

[jasonr95]

had this problem, drove me crazy. every time i hit a bump it would blow a fuse, replaced tail lights, didn't help, finely decided to replace whole harness, to my surprise mice had ate insulation off wire in trailer tongue where I could not see it. just about completely bare wire. do not know how it could have worked at all without grounding out.

 

[Quackrstackr]

The easiest way to check it is to hook to someone else's trailer and see if the result is the same. Same result, truck harness.. no blown fuse, your boat trailer.

The Ram that I spoke of in your other thread blows the fuse regardless of what trailer is hooked to it, so it is in the factory vehicle harness somewhere.

 

[dyurisich]

Question back to you guys......

When I re-ran the wires, I ran them through the tongue, around the frame to lights in plastic wire loom. If there was a bare spot on the brown wire in the loom, would that still cause a short/ground issue?
If its not contacting any other metal how could it?

 

[huntinfool]

It could be touching another wire in the loom. That could be the problem. I need to read the other thread as I asked some questions and I need to see how they were answered. Let me go check that thread.

 

[huntinfool]

OK you need to test this trailer on another vehicle. If it does not blow a fuse on that vehicle then you need to test another trailer on your vehicle and see if it will blow the fuse. My bet is still on the wiring on the trailer.

Test...if you disconnect the trailer and then turn your lights on does the fuse blow then? If it did then the wiring on the truck would be suspect.

Run some tests and report back and that will help us decide how to direct you next.

If the running light wire had a bare spot on it then it should have been fixed. You need to find that spot and cut the wire. Then strip the wire and put a butt connector or a wire nut on it and tape it up good.

Do you have the white wire grounded to the trailer?

 

[dyurisich]

OK you need to test this trailer on another vehicle. If it does not blow a fuse on that vehicle then you need to test another trailer on your vehicle and see if it will blow the fuse. My bet is still on the wiring on the trailer.

Test...if you disconnect the trailer and then turn your lights on does the fuse blow then? If it did then the wiring on the truck would be suspect.

Been working like a dog this week. Will have to run that test to check that and get back to you on that. Thanks for all the good ideas.

 

[huntinfool]

No problem! Thats why we are all here to get help and bounce ideas off each other.

 

[dyurisich]

Hey there everyone. Been a while since I was able to work on the trailer but got her finished today.

Replaced the truck taillight whip connector but was still blowing the running light fuse. Replaced the trailer lights and wires and no more blown fuse. No broken wires on old kit or corroded light sockets. Must have been something internal under the wire insulation?

Was still having a problem with the right taillight after the new one was installed. No stop, and running/ turn was MUCH dimmer than the left. Suspected a ground problem. Solved by running seperate groung pigtail from taillight post to trailer frame. Did the same to left side to keep continuity. All lights working like a charm now.

Thanks for all your input.

 

[huntinfool]

Glad we could help.