Okay, I may be in denial of the root problem being a blend door issue but here is a description of the issue. First I have a 1999 F-150 with 186,000 miles.

The temperature control, heat or cold, will work at whatever the last setting was when I operated the truck from the previous day when I start it the following morning. After about 10 - 15 minutes of operation, I can then adjust the temperature by moving the control **** back and forth. It almost feels like it fills up with air or something that catches allowing the temperature to change. I've checked the **** and it is okay. I had a **** problem on an Escape that I replaced last year. Once the temperature control starts working, it will work the remainder of the day. The next morning, the same thing starts again.

Any ideas or help would be appreciated.

 

is the **** working the actuator motor for the blend door? you can take it out and see if it is

 

A quick update, last night I traced all of my vacuum lines under the hood to see if I could find anything wrong. I found one of the connections loose, it was not off the barb, but at the very end. i pushed the hose all the way back on and the temperature controller seemed to work okay this morning. Since this seems to be an overnight problem I will check it again tomorrow morning.

dnjsyl, the **** did work last night, but the controller was working OK at that time as well. I'll report back tomorrow on the status of the unit.

 

Replaced the potentiometer/temperature control switch and everything is working great now. Thanks you IA Chiefs fan.