Hvac Gone Nuts

[pwall]

Today, the hvac system in my 2002 YukonXL went nuts. The fan will run at top speed, regardless of the temperature settings and regardless if the fan is on or off. Rear defroster also no longer works.

Really weird thing is when I turn of the truck and remove the key, the fan keeps going. There is no way to control it.

Ended up pulling the 25amp fuse from underneath the front hood to shut it down.

Rear hvac seems to be running as normal.

Here is a picture of the hvac I have (the numbers are in celcius.....):

 

Any help you can provide would be greatly appreciated.