On my 2002 screw 4x4 I was having the same problem of AC through the defrost. After spending 3 hours tracing and checking vacuum lines from the firewall all the way through the dash all the way to the climate control. All vacuum lines checked out OK. I took out my climate control (push button electronic type) and remove the vacuum lines from the back. Good main vacuum line. All other switches worked fine, vent / floor / floor-pnl/ defrost ect. I determined it to be a bad switch. I went to the local wrecking yard, got lucky and found an identical unit. Took it to my truck plugged it in and good old cold air started blowing out of vents. This all took me about 3-4 hours and $40.00 to my wrecking yard and I was back in business. In my truck, removing the climate control would take only about 10 - 15 minutes. An easy way to check to see if you are getting vacuum to the unit.

 

i think im having a similar problem, i cant seem to find a leak anywhere. i think i hear a leak inside the climate control head unit.. did you hear anything like that in yours?

 

by the way im also running a 2002 4x4 screw

 

03 F150 4x4 Screw

Anyone know if twhiz is talking about a switch built into the unit or somewhere else.

How would you pull the unit?

 

He is talking about the whole head unit i believe. I dont think you can remove the vacuum acuator out of the head unit.

How did you find one for $40 bucks. Yo got a hell of a deal. Im having the same problem but I dont want to give Ford $480 for a new one. I have been searching for one and cant find one yet. Would a **** style one work in its places instead of the button control? just cuious. Thanks

 

Why does a vacuum line run into the A/C control panel?

 

Because all of the airflow control motors are run by vacuum.

The control unit has the task of switching vacuum to the proper motors based on whatever airflow pattern is selected.

The vacuum motors then move doors or flaps inside the dash plenum to change the direction of airflow.

Steve