I have an 04 FX4 with about 30,000 miles on it.
Lately when ever it snows or rains the heated mirrors come on by themself and there is know way to turn them off without removing the fuse. It kills the battery if I don't remove the fuse or disconnect the battery.
Any help would be appreciated.

 

That sounds like a problem with the ignition switch coupled with a HVAC panel problem.

The power to the coil for the heated backlite ( rear window and mirrors ) should only be powered in the run position, and the ground to is from the HVAC control panel via the Instrument cluster.

If you can replicated it, pull the R04 relay, and check to see if there is power and ground on the coil.



Pins 85 & 86 are the coil.



If you do not get power, change the relay out, and check to see if the symptoms still exist.

 

Still have the mirror problem and now more.
I switched out the rely and nothing changed. I thought it might be a bad ground at G303 so I loosened the bolt and there was a spark and now I don't have a fuel guage(low fuel light on) and my airbag light is on and won't go off.
Checked the fueses I thought had anything to do with the guages, and nothing.
Is there a fuse panel in the engine bay? I looked at the left front fender but they look like relays only.

 

I found the problem and the fix. Ther is a junction box behind the left kick panel and under the parking brake lever. The junction box is bolted together normally. In my truck this bolt was loose. Once tightened all my electrical problems went away.