If I turn the heater or A/C on, I get the air blowing out of the defrost vents... never out of the other vents.. Is this a vacuum leak somewhere? I thought it was my heater control, so I bought one off ebay, but that cable was a bear and I didn't see anything broke on my old one. I did notice a large plug with a bunch of vacuum lines on it... Where the heck do these go?? Any help would be greatly appreciated. Thanks!

Probably a vacuum Leak like you thought, Mine was under the hood pu by the firewall, there was a little check valve close to the center of the car by the heater box...

Hope thats it... (should make your car run slightly better too..)

John

The selection of which vent the air comes out of is controled by vacuum. If you hear a vacuum leak in the car then I would first check the control that you use to select vent heat etc. If you move the **** slowly you should hear the doors that deflect the air, open and close. yes you should have the car running . This **** has the all those vacuum lines on the back as you saw. There is a plate in behind the white thing that the lines connect to that directs the vacuum. I have found that this becomes worn and lose. You can try to press it together again or get a new one from the dealer.

The default location for air flow is the defroster vents. If there is vacuum leak that doesn't allow the actuators to change the air flow, it defaults to defrost. Check all vacuum lines that connect to the controller. My wife's 93 Z28 had the same problem and I found the main vacuum line fell off the charcoal canister. We had other issues also, like on a long trip, the brakes would lose pressure and she needed to pump the brakes to rebuild the vacuum. City driving was OK since the brakes were used regularly, but the long drive home, with the AC blowing out the defroster vents only and the brakes acting up, my wife was ready to sell the car!

A Bad Master Cylender Would do the same thing...

John

Thanks for all the help.. Will check it out this weekend while I change the door handle... Also I have the only PINK camaro on here.. that could be good and bad.. lol

I was thinking that at the time, but the problem was solved after I reattached the main vacuum connection. It was the cheapest repair I've done to a car in a long time. I even called and got estimates on a master cylinder before I found the vacuum problem.

Well I did some work on this vacuum leak today.. I found a little round thing that goes through the firewall right above the master cylinder and below the canister... It was not connected and was actually broke in half.. That piece goes into a T where 1 goes to the wiper pump (which it runs, but no fluid comes out) and the other looks like it goes over on the passenger side into the firewall? I don't have any vacuum anywhere in these lines... don't know what to do from here..

What you have found is the windshield washer lines. If one is broken then that is why your washer does not work. There is a black vacuum reserve that is near where you are looking that has a vacuum line from the intake manifold going to it. then the outlet of the reserve goes over to the passenger side of the firewall and into the interior. Do you have a vacuum pump? To test the vacuum lines in the interior get a pump and create vacuum on the line from the reserve. (You can try sucking on the line) If there is no vacuum move the vent selection control on the heater control to see if one position can give you vacuum. If not then you have to get at the heater control and see if a vacuum line has fallen off of if the control value is not sealing.

Thanks! I will give that a try this weekend.. I have a vacuum pump... I did find that black canister that you mentioned. It was mounted on the firewall right above the master cylinder/booster.. I did have good vacuum there. Thanks again for your help.

I believe that even with everything turned off, there will be a minimal airflow through the defrosters. This is done to maintain positive cabin pressure to help keep exhaust fumes out.