Howdy ya'll,
After unloading the truck after a fishing trip today, my mother in law mentioned to me that the headlights were on (daytime, "auto" selected on the switch). I thought they might turn off after a few minutes. 20 minutes later I return to the truck and the head lights are still on. I turn the switch to "OFF" and try to start the truck, and it won't crank at all. The DOOR AJAR light is on, and I hear a very rapid clicking noise coming from the passenger side dash (a relay I believe).

I'm thinking whatever switch/relay turns the AUTO headlights off after the doors are shut didn't function, and drained the battery. I installed an aftermarket stereo system back in 2005 that has been acting up lately, but I don't think that's what the issue is. I read a few threads about door switches sticking open leaving electrical power on to the radio and lights, and this sounds similar.

Battery is an Interstate, about 4.5 years old, currently on a charger.

2002 F150 SuperCrew; 115,000 miles.

Any ideas?

Thanks in advance!

 

Got the battery charged and truck started. Drove it about 4 miles, checked all the interior and exterior lights, radio, 4x4 hi, 4x4 low, windshield wipers. I didn't check the electrical driver's seat or mirrors. Everything looks/feels good.

The headlights will not turn off! All the headlight switch positions feel right with a solid click and everything, including pulling the **** out in the ON position for the fog lights. Here's what's happening:

Auto - All exterior lights are on (as the should be, it's dark outside)
Off - All exterior lights are on (headlights, tail lights, parking lights)
Park - All exterior lights are on
On - All exterior lights are on (pulling **** out turns on the fog lamps)

After I drove I turned the truck off, turned the lights switch to OFF. The exterior lights and instrument cluster lights stayed on, so I disconnected the negative battery terminal.

These fuses/relays are below the steering wheel which I'll check tomorrow:

Relay 5: "Daytime Running lamps," though I don't think I have that option since I can just turn the lights off with the switch.

Fuse 14: Battery saver relay / interior lamp relay
Fuse 27: Foglamp relay and indicator / main light switch (upstream)

There's also a main light switch fuse under the hood.

It seems to me if a fuse/relay failed the affected component would not work at all. What would cause the lights to turn on and NOT BE ABLE TO TURN OFF?

 

Checked all fuses under the steering wheel and at the power distro box under the hood, no blown fuses. #6 under the hood (main light switch/park lamp relay) was fine.

 

Pulled the Parking Lamp Relay fuse (#3) and main light switch fuse (#6) from under the hood and those kill the lights. Sounds like a relay is going bonkers in that fuse box when I plug them back in, hopefully that is where the problem is.