I have a 2004 Grand Prix. The air system is not zoned.
Earlier this summer I noticed my air wasn't working. I got a can of AC charge stuff from AutoZone which has worked for me in the past, but it had no noticeable effect. I was only getting heat. So I brought it in to a shop and they said that the AC system had no pressure at all. They filled and flushed the system two times trying to find leaks but no luck, and said if there is a leak it is very very slow somewhere they can't see.
Still, after recharging the system, I'm only getting (moderately) cold air on the passenger side. They believe it is that there is a heater door stuck open somewhere mixing with the cold air and that's why the drivers side is all warm air.
I should also note that for quite awhile now I have air flow through the vents when driving even if I have no air/heat turned on. The faster I drive the more air flows through but it isn't very much, almost like it's turned on to the lowest setting.
Also, there is occassional high pitched sqealing come from a fan on the passenger side. It increases in volume and pitch when the fans are turned higher. It will eventually stop, and often doesn't happen at all, but the fan is still blowing.
Also, just in case it's pertinent, this past winter my blower motor resistor failed and the fans would stay on even if I tried to turn off the heat, and even with the car powered off. I had a bad battery so it killed my battery a couple of times if I didn't pull the fuse each time I left the car. I replaced it and that problem stopped. I have no idea if it related to the AC issue as I wasn't using it at the time of course.
That's all I can think as far as things that relate to the air system. I hate to bring it back to another mechanic as I don't have a local trusted guy yet, and likely pay for diagnosis and no solution. I also wouldn't much mind a temp fix if it is the heater door, such as keeping it manually closed for the time being, if I could figure out where that is.
