heater/ac fan stays on when ignition is off

[yodadoordonot]

92 Explorer Sport, V-6, 5 spd with 140k miles

I occassionally get a burnt wiring smell when I have the ac/heater blower fan turned on high. The smell stops if I turn the fan down to one of the lower speeds.

Just recently, however, the blower fan has started staying on when I turn off the ignition switch. I have to manually turn off the fan switch also, or the fan will continue to run.

Seems like maybe some contacts have finally welded themselves together. Is there a relay that controls this or is the ignition switch the culprit?

Thanks!

 

[88vert]

There is a 50 amp fuse for the heater motor.Are you hearing any squealing coming from the motor that is the first indacation that your motor bearings are going out.