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Discussion Starter #1
Well, I've been round and round with this issue for about 3 months now. Here's the issue:

My HVAC has been acting a little....touchy for the last 6 months. By this I mean it doesn't respond to certain commands, especially the "off" button has become near impossible to get it to turn off when pressed. In the past 3 months though, a much more serious issue has began to occurr. For whatever reason, the HVAC has a mind of it's own, sometimes blowing defrost, sometimes blowing feet, and SOMETIMES blowing as it's set to(out the vents, etc) Originally we thought one of the actuators was bad under the dash. Oddly enough though, when i pulled them both out, took them apart, and manually powered them, they worked flawlessly. It still just sort of decides when it wants to blow out the defrost, or out of the vent. I was told this is an AC controll module issue. I really REALLY don't wanna stick down $700 on a new one. Certainly this is not it, as it still is switching back and forth. It makes me think there has to be a bad vaccuum somewhere, that is sporatically getting vaccuum?! Is this possible????? I would think if the AC module went bad, it would never work. I will say that no matter whether its on defrost or through the vents, it does not lose the AC temp, as the front windshield will begin to fog up when it gets stuck on vent :mad:

I just want my consistent AC back!!! :rant2:
 

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White Diamond '03 DHS (with DTS floor shift)
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Sounds like a vacuum problem to me. Defrost is the default mode when you loose vacuum. Does it switch modes when you step on the gas (low vacuum)? What year is it? Earlier models had vacuum operated parking brake release and when the diaphragm went, it would cause a problem as the brake release system is on the same vacuum circuit.
 

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Discussion Starter #3
the car is a 1996. I have tried kicking in the gas, and it seems to make no effect(at least none i can tell). this might sound crazy, but if you slap the center console(approx. near where the glovebox meets the HVAC center, it will sometimes kick back in the vents like it's supposed to, haha. Why, I will never know, haha
 

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White Diamond '03 DHS (with DTS floor shift)
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Start with the parking brake release diaphragm. It is at the end of the circuit. Make sure that the diaphragm will hold vacuum. If that is OK, then work your way back and check all the vacuum line and connections.
 

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White Diamond '03 DHS (with DTS floor shift)
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Bigbird, check your FSM. It is referred to as an HVAC system.
 

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Discussion Starter #8
thank you Ranger....And to you too Z0no.....


Update: Ranger, so i got to fool around with it on the way to the airport this afternoon. The E-brake seems to not be working properly either. I know for a fact i have checked it earlier(from reading/researching other threads about problems with the HVAC system), and it worked properly. I am beginning to feel a vacuum line is the issue, or maybe that's just hope, haha.

Today, on the way to the airport, the AC switched back and forth.....3 times in 30minutes of driving. I stopped both when the HVAC was operating properly, and when it was defaulting to the defroster. Both times, the Ebrake would engage, but not disengage when put into gear. I never turned the car off(if this matters).
 

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White Diamond '03 DHS (with DTS floor shift)
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I think you are on the trail. Pull the vacuum line off of the parking brake release diaphragm and plug or tape it. Then take the car for a ride and see if it operates OK. My guess is it will. If so, the diaphragm is bad. You can verify that by putting a hand held vacuum pump on it and draw a vacuum and see if it holds. No vacuum pump? Put a hose on it and suck it down and see if it holds.
 
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