heater fan will not turn off.

[DanTheMan]

Hello,
I have a 96 Mark 8 that the heater fan is continuous on high. No matter what you do with the heater controls, the off button does nothing. All the different options like defrost, vent, floor work the display works in the heater control etc. I just bought another heater control unit and put it in and same result. As soon as key is turned to on the fan starts blowin. So is this controlled by the cars computer? Thats my next thing to try and replace. Thanks. Dan

 

[joegr]

I would suspect the blower speed controller, often called the "blower resistor." Probably either the transistor in it has shorted or the bypass relay is stuck closed.

 

[DanTheMan]

Darn it, that should have been obvious to me, I will test that relay and look for the resistor you are speaking of. Thank you!!!

 

[joegr]

Darn it, that should have been obvious to me, I will test that relay and look for the resistor you are speaking of. Thank you!!!

It should look like this.

The relay is inside the assembly.