I havent driven my C4 since before Christmas but ive been starting it regularly and keeping it snow free. Just started it again but the air con and demister isn't working. Could it be frozen?
Comments summarized into an answer:
Further comments indicated that the Heating, Ventilation and Air Conditioning (HVAC) fan was inoperative.
There are two types of HVAC fan control systems.
- the simple blower resistor system (which generally offers three or four discrete fan speeds)
- the more expensive infinitely variable system ( which uses Pulsed Width Modulation [PWM] to control fan speeds.) This style of blower controller is pretty robust for the life of the car. Its just a pretty expensive option.
The simple system uses a resistor block which also contains a thermal fuse. One the fuse goes, you have to replace the entire block. This is a great first time do it yourself repair. The part generally runs $10 to $13 USD or so. Generally the block is mounted in the HVAC unit behind the glove box on the passenger side of the instrument panel. You are going to want to purchase a repair manual (Chilton or Haynes) so you know how to remove the kick panels and/ or glove box to get to the resistor block. Remove a wire connection, remove a few screws and replace the resistor.
I suspect that thermal fuse (also called a thermal limiter) is blown.