I have an 07 fx4 with manual climate control. Randomly while driving the fan will shut itself off (usually when on the 3 or 4 setting). When it shuts itself off if I switch the dial to zero then back on it functions normally again. Any ideas on what is causing this?

 

Blower motor resistor...?

 

The switch in the module might be acting up as well. I've noticed the opposite problem on mine. Some mornings when I start the truck with the blower off, it will still blow full blast for several seconds before it shuts off.

 

that's what I thought at first but why would it work on any speed not just high? Also I'm no electrician.