Been cold here lately...last time I drove my '08 F-150 Screw Limited, I noticed that the heat never came on, even though I had it set to "Auto" as always. Instead, the auto climate control blew only cold air thru the dash A/C vents. No matter what my selection for air flow, or for air temp, I only got cold air thur the A/C vents. Auto setting, heater setting, defrost setting, bi-level setting...no matter. The only thing I got was cold air, thru A/C vents on the dash.

I did notice some very strange clunks and squeaks whenever I changed the selection from "heater" to "defrost" to "bi-level"...

Turns out it was a bad battery. Who'da thought a weak battery would cause the heater not to work. Turns out the battery, even tho strong enough to crank the engine, was not strong enought to maintain power to the blend door actuator motor. Consequently, the blend door stayed on cold. A new battery cured the heater problems.

CW