Fog Lights/Back Tail Lights won't turn off when key is out if ignition.
 

Can somehow who is a mechanic please tell me what is wrong. I'm just a dumb old woman. I have a 1999 F-150 XLT (Super Cab) truck. My son, who is a mechanic, normally does all the vehicle maintenance, however, he is getting ready to leave for Basic Training for the National Guard. About a month ago, I rented a U-Haul trailer, and when they connected the trailer, I got the trailer home, turned off the ignition, took my key out, my fog lights and tail lights wouldn't go out. I believe it did something to my truck's electrical system. My son plugged the diagnostic tool in and that told him it was probably the headlight switch that blew out. We got another one from Napa Auto Parts - he put it in. Everything was fine for a month, then a couple of days ago, he was driving the truck, turned off the ignition, took the key out - same thing. Could it be that it is just a bad headlight switch, or could it be that the U-Haul trailer shorted something out somewhere in the truck? He checked and followed all the relays and all the relays are good. I am going to call NAPA tomorrow to see if they will give me a new headlight switch in exchange. Perhaps this switch just went bad. We are at our wits' end. Thanks for any help, advice or if someone knows exactly what is wrong - I would greatly appreciate it.

have you tried unhooking the posititve battery cable to let the cpu rest itself......? might try that

When the U-Haul folks "connected the trailer", how did they do it? By that I mean did they use the factory trailer connection or did they - as some of them do - hack into your wiring harness and Scotch-Lock you a trailer pigtail? Since your problem apparently started with that event, I'm leaning towards something back there causing a short that may be frying your switch.

First of all, welcome. You may claim to be a dumb ol' woman, but at least you knew enough to ask the right folks for advice. :)

If the u-haul dealer hooked into the factory connection plug on the bumper (like they should have) I would be surprised if that's causing your problems. The trailer lighting circuits areon their own dedicated wiring, and once they're disconnected shouldn't have anything to do with it.

The only thing those the fog light circuit and the parking lamp circuit have in common is the headlight switch. It's quite possible that yours is bad again, but it would be a shocking coincidence. Without being able to check a few things, it's tough to say for sure where the problem lies exactly.

Thank your son for me. [waving my flag]

-Joe