Heater Problem
 

I have a 2008 F150 and there is a clicking sound when the heater is on. This has been going on for a couple of months and when I took it to the dealer they could not hear it. Now when I turn on the heater it is blowing cold air so I have to turn it all the way up and then I can not turn it down when it is getting too hot so I have to turn it off. I notice even when I want the heat on the floor it comes out of the vents on the dash. Anyone else having problems?