Hey Throttletune or any other mechanics, I have one more question about my sons 93 Cavalier. The heater and AC all work well, but it only blows out of the AC vents. It wont switch to the defroster vents or the floor vents. When I got the car a year and a half ago, the guy I bought it from said the only thing that did'nt work was the cruise control. Everything checked out, I finally found a vacuum leak (believe it or not the car ran fine). I replaced the busted hose and replaced all the vacuum lines in the car. Now you have a short history, anything I should look for, let me know.
Hi Ranger, Coming off the throttle body, there is a vacuum line that goes through the firewall to the A/C. You will know it's the right one if it tees off and goes to the purge solenoid. You can ID the right solenoid by making sure the line from the solenoid goes to the carbon cannister. Make sure the line to the A/C is getting good vacuum, and you may need to pull the heater control to make sure vacuum is intact to it. Seems to me that when it loses vacuum, it will default to defrost though. But, that is the first check on the list. Should have vacuum to the violet line to the control. You can run the car, jump a vacuum line to the control with a short length of vacuum line and work the control to make sure vacuum comes from ports of the control assembly. If that's the case, then you can jump the harness from the purple to each individual line in the harness to make sure each door operates. I actually use a vacuum pump when going to the individual lines to make sure the door operates and vacuum holds ensuring their integrity.
I remember a car i had years ago that did aboutthe same thing, come to find out a pen had fallen into the vents through the defrogger on the dash, lodged in the "valve" that redirected airflow....might check and see if you can move the flapper or "valve" by hand.
Thank you Mr Thottletune, your always so helpful. I took his car to work today, and as soon as I got it to highway speed, it switched. I wonder if there is a resriction or a kink in one of the vacuum lines. The high temp today is 25- degrees, so this is one problem thats going to wait a while. It'll get fixed because I am a picky SOB, but it will wait for slightly warmer weather. I figured it switches at highway speed so I put it on Floor/Defrost, that will get me by for a few days. Hate this stupid cold front. I hate the cold.
My pleasure Ranger. I think you're all over it, and I think you are correct as far as a pinch, or possibly a pinhole even. Cold does suck. But, I guess I have to suffer some of that to live in paradise.
