Trailer turn signal gremlin

[hheynow]

The #6 position red 10 amp fuse in my power distribution box keeps burning out. It's related to my trailer light turn signals. When my headlights are off both left and right trailer turn signals work properly but when the headlights are on the #6 fuse burns out. Where should I look for a bad ground or a short?

 

[Ford_Forgotton]

This only happens when the trailer is plugged in? What about with just the parking lights on? My guess would be a chaffed wire somewhere on the trailer. Most likely at a bend or joint where the metal is sharp.

Are you using a 4 pin harness, or a 7 pin harness on your trailer?

 

[hheynow]

This only happens when the trailer is plugged in? What about with just the parking lights on? My guess would be a chaffed wire somewhere on the trailer. Most likely at a bend or joint where the metal is sharp.

Are you using a 4 pin harness, or a 7 pin harness on your trailer?

I use a 4 pin and the harness is new. It only happens when I'm plugged in and use the turn signals when my headlights are on. So you think it's on the trailer and not in my truck's wiring?

 

[Ford_Forgotton]

a 4 pin plug is "left turn/brake", "right turn/brake", parking light, ground.

The difference between head lights ON and headlights OFF is the parking light signal.

Thats why I asked if it would blow with just the parking lights on, and not headlights.

You could try OHMING out the trailer harness. You should see continuity on the ground pin, and some resistance on the parking and turn/brake wires. Then try OHMING between each pin. There should not be any continuity or OHM readings BETWEEN pins.

Edit: well, there should be some readings between the ground pin and the other pins, but not between each brake/parking pins.

Then do teh same on the truck.

 

[hheynow]

Thanks for the info. I never though of testing it with just the parking lights on. Since I don't own a trailer I'll OHM it this weekend when I'll have some free time.

 

[Ford_Forgotton]

oh, this problem happens even without a trailer? Or did you borrow someones? Its possible the truck is wired wrong, or the trailer you borrowed is wired wrong. I thought this was on a trailer you had hooked up right now.

 

[hheynow]

oh, this problem happens even without a trailer? Or did you borrow someones? Its possible the truck is wired wrong, or the trailer you borrowed is wired wrong. I thought this was on a trailer you had hooked up right now.

Without a trailer with the #6 fuse removed everything works fine with the headlights on or off. Yes it was a borrowed trailer and yes it's very possible the trailer had a short or was wired wrong.

 

[Max Power]

I am with Daryl. It is probably the truck or trailer wired wrong.

4 wire plugs always use the same colors.

white - ground
green - right turn
yellow - left turn
brown - tail lamps

I would use a battery charger or a battery (make sure you use a fuse) and test each of the 3 circuits and see what happens. Then try tail lights on and then try each turn signal.

You should be able to get a good idea what is going on from that point. If all test well, start testing the truck.

Good luck, post here if you have any questions.