I have a 97 F150 (59Kmiles). Has anyone had the defroster fan operate by itself? I was getting ready to go to work and as I approached the truck I noticed an electrical fan running. This turned out to be the fan for the defroster. What I find incredible is the truck was locked and the ignition was turned off. Some time during the night the fan turned itself on. What really worries me is the potential for fire. Let me know if anyone's experienced this one. I went to the dealer and got that are you sure that really happened look.

 

Sounds like a short somewhere, maybe wire insulation has rubbed off? If I were you, I'd take it to another dealer, one willing to track the problem down.

 

>I have a 97 F150 (59Kmiles). Has anyone had the defroster
>fan operate by itself? I was getting ready to go to work
>and as I approached the truck I noticed an electrical fan
>running. This turned out to be the fan for the defroster.
>What I find incredible is the truck was locked and the
>ignition was turned off. Some time during the night the fan
>turned itself on. What really worries me is the potential
>for fire. Let me know if anyone's experienced this one. I
>went to the dealer and got that are you sure that really
>happened look.



Hello
I had the same problem and dealer found out my windshield leaked on to a module under driver side somewhere.

 

You've probably got water from a leaky windshield getting into the fuse box causing it to short inside. I've seen quite a few of these and usually the fan staying on the complaint. You might be able to dry out the fuse box with compressed air but it seems that most of the time after they've had water in they have corrosion too and need to be replaced.