When setting is on ac low or max the fan blows out the vents for about 2 minutes then quits and blows thru the defrost vents for about the same and switches back

 

Are you saying it does not do this if on fan speed 2 or 3?

 

Check the white vacuum hose leading to the recirculation vacuum motor located on the passenger side of the engine bay. Very common problem. This time of year we see posts several times a week.


A recent post with pictures: https://www.ford-trucks.com/forums/1...lleration.html

 

Yes does on all speeds thanks for the reply will check it out

 

Yeah you most likely have a vacuum leak or leaks in the system that tells the doors what position to be in.

 

How do get to the door, it still has those plastic lines that are probably leaking. I have replaced all others but the two that go to door?

 

What door are you talking about?

 

The one that controls between the vents and defrost

 

I first replaced as much of the brittle white vacuum line and that helped a little. Then I replace the vacuum motor and that helped a lot. Still a very slight problem but I can live with it.

 

It's behind the radio and the a/c control panel I believe.

 

So you checked this one mentioned and it was ok? The tubing could be cracked/ broken inside of the harness. Does the door actuator move when you change settings?

 

It was disconnected , I reconnected it, No when i change settings it doesn't help.

 

Check and make sure the check valve in the vacuum line going to the tree and the vacuum tank is hooked up.

 

Didn't see a check valve , replaced a portion of the black tube going to the dash, it helped but still switches.

 

Maybe photos will help.




1992 But you will get the idea.
Attachment 287666

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