Help a girl out , I can't seem to fix this and you guys may be able to ride with windows down but my hair won't let me. My air cond. goes to (defroster) when I press on gas. At Idle does fine and comes out vents. Just started this, I have looked at a bunch of my vacuum hoses and don't see any cracked. Any way to test or see where the vacuum leak could be or where to really look harder???

 

Vent control might be cable operated... maybe your pedal is moving the cable to the door? The gas and A/C are totally unrelated systems

 

If you don't find a line with a leak, it could be the valve. Looks something like this -

http://www.partsgeek.com/793z5wz-for...+Control+Valve

I fixed the actual bad line and still had the 'go to defrost', it ended up being this valve. If you remove it, I think you should be able to blow through it but not pull air back through it (I may have it backwards). In any event, air can only go one way through this. If you can both blow through it and pull air through it, that is at least part of the issue.

cadtdi

 

Passenger side of the engine compartment, near the firewall. Air mixer door control valve.

There's a picture and a good write-up about it here...http://www.fullsizebronco.com/forum/...ents-dead.html

 

Where is the Vacuum Control Valve?

 

that valve is visible around the middle top of the engine, you have vacuum line running into it/out of it.

I can take a pic when I get home later, thought I might have one handy but no.

 

A picture would be great. Is it on the line that runs to the throttle body?

 

Click the link a couple of posts up to see a pic.

If you are looking at your engine compartment, it is on the passenger's side of the intake manifold near the firewall. There is a vacuum hose running from the manifold tree to it, with two more vacuum hoses coming off of it - one to the A/C and one thru the firewall bundle on the passenger side.

 

Alright I got the check valve from ORileys for like $8. I will replace it in a little bit when it cools off. Sorry to ****** the thread but if this fixes my problem I will let y'all know so it could help others. Thanks so far!

 

Didn't fix my problem...but it helped! Doesn't do it as often