Any one have an idea on why the ac will swithc from vents to defrost vents when its on max AC. It will run normal for about a min then go to defrost. Doesnt matter if going uphill or downhill for higher or lower vacuum. In Normal AC it fine. Any sugestions are appreciated. You can reply here or at my aol accout which aszabo7369(No Email Addresses In Posts!)

 

sounds like the door for panel/def is moving instead of the recirc door. Do these things have vacuum doors or electrical? it could be that a hose is just on in the wrong place. when you set the **** to defrost, does it work correctly?

 

There vacuum. Nothing has ever been disasembled. Yes it works correctly in defrost. At first I thought it could of been a vacuum leak but dont think so.

 

I have a 2001 SuperCrew and when I set my mode to floor/dash for normal venting the AC somehow is activated. It blows cold air like the AC was on. However, when I sent the mode to just dash it vents correctly. I know the compressor runs in defrost and AC mode, but why is it running in floor/dash mode? Any suggestions?

 

are you sure its not a vaccum leak? After putting the new motor in my 1997 4.2L, the vents would only work on defrost. We found out it was a vaccum leak and once found, the vents worked fine. I would check it out if i was you.

 

Grandblanc, it is normal for the a/c to run on floor/vent. This is so that in the winter, when you go to turn on the heater, the compressor comes on momentaraly to keep things working. It also lowers the humidity in the cab on cool damp days.
Jimmy

 

lxman1, thanks for the insight.

 

Can anyone post a vacuum diagram for 1997 f150? I have a
leak and found hoses diconnected/busted and dont know where they go. A/C comes out defrost only. chilton does not show and
sticker is just for emissions type vacuum. PLEASE its hot in AZ.
THANKS