I usually engage in the '73-79 forum or my local chapter but...I just picked up a 2004 F150 FX4 Supercab, I had a safety inspection done and am working through some of the issues. What I thought would be an easy fix has me scratching my head....
The turn signal indicator on the passenger side mirror is not working(front and rear indicators work). I took the mirror apart and get no voltage to the led array, next I pulled the rubber boot off of the harness in the door jam and probed the wires while with a test light and found one of the wires would blink the test lest light but the colour didn't match the the turn signal array, it matched the heated mirror wire. I probed at the heated mirror connector at the mirror and sure enough it blinks! WTF? Then i notice that the heated mirror indicator light on the center dash is blinking? I push the heated mirror button below the indicator light and ALL turn signals (front and rear) stop.

I searched the forum for mirror turn signal issues and found a thread about corroded wire splice below the fuse panel. I checked and have no splice all look ok so I thought I would post and see if I can get some direction or a schematic.

The symptoms are :

_Passenger side mirror turn signal(right turn) indicator does not work
- front and rear turn signal indicators work
- power seat works
-fuses are good
- drivers side all turn signals work fine
- heated mirror indicator light on the dash blinks with the passenger side turn signal
- pushing the heated mirror button when turn signals are flashing (right turn) results in a solid heated mirror indicator light but all other right turn signal indicator stop blinking (off)


Any help would be appreciated. It seems to me that there must be a short between the two circuits but where?

Thanks
Frank

 

I think you are right. The two circuits are crossed. Have you checked the plug for the heated mirror switch? The passenger side mirror turn signal might run through there.