Join Date: Nov 2008
Location: Winder, GA
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Do you electronic A/C (buttons) or manual A/C (dials)? The above document may apply to you as well.
Vacuum leaks are hard to hunt down, and may not always be the problem. A bad solenoid/diaphragm on a vent door could be the issue as well. Do you hear any "hissing" under the dash? You may have to get your head up under there and give it a good listen, and even then it might be difficult to find anything.
In the past, I've found it may be easier to remove the vent control form the dash, disconnect the vacuum hose header from the control, and then check that we're getting vacuum at least that far. Then with a small piece of wiper tubing, we can run a line from the main vacuum input to the different ports on the header to see if the vent registers function correctly. If you have vacuum and everything functions correctly when checking manually, then the control is bad. If any of the registers don't function correctly when checking manually, then the solenoid/diaphragm for that register is bad or the tubing is broken.
Under-dash stuff isn't fun, but take it one logical step at a time and it's not too bad.
Friends don't let friends drive JUNK
2001 7.3L - Stage 1's at 399 HP - Just a lonely Daily Driver
2004 6.0L - Studded - 440 on #2 Only - 482 on Water/Meth - 12.961 @ 102.6 MPH