Trailer Battery Not Charging When Towing Behind 2006 Ford F-250

Updated 04/05/2010 | Published 04/03/2010

Question:

I have a 2006 F259 HD. Under the hood I have red, blk, blue & white wires coming out of harness, but not hooked up. Truck has factory brake control.Everything works but does not charge the battery in 5th whl trlr when towing. What needs to be wired under hood and do I need relay? Thankyou

asked by: Rick A

Expert Reply:

If all the other functions work, I doubt the 4 wires you found need to be hooked up. It sounds as though those wires may be for adding an aftermarket brake controller if you did not wish to use the factory controller.

I would use a circuit tester, like part # PTW2993, to check the 7-Way on the truck. As you look at the 7-Way on the truck, the pin in the 1:00 position is the 12V power supply. This should be hot when the truck key is in the ON position. If it is indeed hot, then you have a problem with the trailer, most likely a dead battery or a bad ground connection. It could also be that the trailer connector is wired for power on the center pin, which would actually be the reverse circuit on the truck.

If you do not have power at this pin with the key on, then the problem is on the truck. I would check the fuse panels on the truck. This pin should be on a fuse or circuit breaker. Check to see if a fuse needs to be replaced. Trace the wire from the connector as far up the truck as you can. Look for frays or nicks. Finally you may have to remove the 7-Way and open. Sometimes the insides can start corroding, green or white build-up, and cause a circuit to short or break.

Write back and let me know what you find and we will go from there.

expert reply by: Patrick B