When my 1999 Ford Expedition is turned off and sitting there, even for hours, the defrosting fan comes on by itself. I can feel cold air coming through the vents inside the car. The fan will turn off if I turn on the key or even if I step on the brake pedal, with the car still off. It won’t stay off until I disconnect the battery. It seems to occur only when the temperature drops, like below freezing (coincidence??). The other day, I left the fan running for several hours, it never turned off, I then disconnected the battery. It ran the battery down. Randomly/intermittently the dashboard clock, windshield wiper, or radio won’t work when the car is running. I recently bought a new battery . I recently replaced the outside mirrors. Also, the passenger side window won’t go up or down using the passenger side control but will using the drivers side control. Is my car haunted or what?? This is the car challenge of the year.
Sounds like the GEM module.It’s mounted to the back of the fuse block under the dash if I remember right. You could try unplugging the connectors and make sure they’re clean and no pins have backed out.
Do you have an aftermarket alarm or remote start in the vehicle? Could one have been installed prior to your ownership if you didnt buy new?