I got a 99 powerstroke and my ac only blows out of my defrost vents. Pump runs and when ever I putty finger over nipple on vaccum pump it stops. Can't find any leaks.


Thanks
Adam

 

I had that problem, it's the valve that does open in your vent in the dash

 

Ok.is it the blend door?where's it located under the dash

 

The blend door only controls cold to hot on the temperature setting. The door that you are looking for is the mode door, that's the one that controls vent operation. It is mounted in the heater/ac box and there should be an external vacuum motor. You said that the vacuum pump is running and shuts off when you put your finger over the nipple. Does the vacuum pump shut off at any other time? That pump has actually got three nipples on it. One of them is on the side of the pump and the other two are on the same vacuum circuit and should be coming off of the end of the pump. A vacuum hose should be run off of one of the 2 ended nipple and run to the one on the side. That is a switch for the vacuum pump to shut off when it achieved about 15 inches of vacuum. If the pump does not shut off at all unless you place your finger over the nipple, then you do have a vacuum leak somewhere. Double check all the vacuum lines and also with the key on and the engine off, listen up under the passenger side of the dash while you turn the mode selector from dash to defrost to heat or mix. If you hear any vacuum sound at all you do have a leak. There should also be a vacuum reservoir somewhere in line with the hose that comes off of the small electric vacuum pump that may have a problem.

 

Could it be as simple as a fuse