Air Conditioner problems...

I'm a california citizen. Needless to say, summer is right around the corner, and the air conditioner is giving me a problem. I noticed when I purchased the blazer back in october of last year, that the air conditioner didn't blow cold air. My thought was that it might be out of Refrigerant. I put a whole can (THE BIG CAN, NOT THE SMALL REGULAR SIZE ONES) of refrigerant in, and I noticed that it was low before i installed, and normal after the install. I got in the blazer, VUALA!! Cold Air! I figured I installed the AC coolant myself rather than taking it to the dealer to charge me about 100-150 bucks to do it. I laughed. I laughed and I laughed. Well now, a few months later, I still get cold air (Although it might be low AGAIN!) but here is the thing. As soon as I start getting on the freeway, obviously you have to speed up. I hear the engine rev, and all of a sudden, I can hear the air conditioner work overtime except, it's not coming out of the ac vents anymore. Its coming out of the top vent, and the bottom vents. The front vents no longer blow air. As soon as I hit 70-80 and the transmission switches gears, the engine runs smoothly, and the air conditioner Returns, blowing cold air. I don't want to have to take it in to the mechanics, and I'm wondering, does anyone have a clue WTF I'm talking about? some help GREATLY appreciated. Also, I think I might need to clean the condensors, but that's the least of my worries right now. I want to know, why it is that when i'm forcing the engine to pick up speed, the AC quits blowing air, but returns as soon as I'm smooth riding.

You have a vacuum leak, that's why the HVAC is changing modes.

Yip, check all the vacuum lines going to and from the engine intake.

Especially the lines going to the vacuum ball.

Right on the F**king DIME!! :smokin: :smokin: Is there anything the people on these forums can't fix?

Perhaps you guys can help me get a chick while i'm at it!
:grinno: :iceslolan

Thanks alot guys, I do have a leak.

I more or less have the same problem. I figured that it was a vacuum leak; and did find two pieces of line (near the vacuum ball, no less) that were rotting and are now replaced. I've tried to follow the other line; and haven't found any other "obvious" problems.

Oddly enough - my system is still stuck on defrost. I do however, now get some flow from the lower vents...????

The bottom line: What is the best way to chase down a vacuum leak for the climate control system?

I took apart the panels under the dash and tried to follow and "look at" the hard plastic color-coded vacuum lines that run the system. The all "looked" ok; but how do I really know; and where should I start?

I'd appreciate some advice, since I'm just a weekend mechanic.

BTW - I also get the most generic EECS error from time to time; and I figure that it might be due to the same problem source...????

The bottom line: What is the best way to chase down a vacuum leak for the climate control system?


the best way would be to take it to a mechanic who specializes in A/C. Polar Bear In sacramento does it, but they are always booked, and I have to wait at least a month before I can schedule an appointment with them. So, The other best way would be to by the Dye that you can put into the A/C, so you can spot leaks. it's called the R-134A Stop Leak & Detector, usually $5.99 at Autozone. Instructions should be included with the can. I think you need like some special light to view the leaks. this is the only way I know to spot a leak you can't see. Anyone else have a better suggestion?

How's putting dye in the A/C system gonna help him find a vacuum leak? :)

I think we are talking about two diffent things. As far as I understand it, the climate control swithc uses vacuum to select between the different modes - mine is stuck in the Defrost mode.

I had heard that this is often caused by avacuum leak - quite often in the main vacuum feed line that goes to the switch.

Mine "looked like it was OK; but it was hard to get a good look at all of it, since it is buried under the dash.

I did find where it comes out of the firewall; and the rubber vacuum line that feeds it, along with the line that goes to the vacuum ball were rotting away; so I replaced those, hoping that it would fixed the problem - it did not.

so, now I am faced with chasing down a not so obvious (and probably hard to reach) vacuum leak.

So, I am trying to determine two things -

1) is there something else that I am missing, other than a vacuum leak
2) if it is a vaccum leak - what the the most typical one(s); and what is the best way to chase the vacuum leak down.

I am currently having the same issue and now have almost the entire dashboard out. Right behind the selector switch I have five vacuum lines; grey, black, brown, orange, and blue. My grey line does have vacuum so vacuum is going to switch. I can jump the grey to the orange and one of the acuators will engage ( the one that pulls air from the cab instead of the outside ). But the blue, brown, and black lines do nothing. The blue line goes to an actuator behind the radio. The orange line goes to an actuator on the bottom passangers side. The other two heck if I know. Anyhow I am so stumped as to the problem any help would be helpful. B.T.W all of my lines hold pressure as I can pressurize them and they stay that way for some time with the exception of the black and brown which appear to be connected in what I believe is a push pull setup. I have vacuum to the switch, I don't have a leak ( that I can find ) but only the one actuator actuates and still no air out of the front vents just the defroster and a little on the floor.

Granted, I'm no mechanic, and some stuff just flies over the top of my head, I tackled this problem and lost. So, I took it to the nearest midas. NO BULLSH*t, I called a day before, and made an appointment. I walked in, the following day, told them what my problem was, and they automatically told me, "That sounds like an electronic problem, we might not be able to fix it." so, they pull it in, open up the hood, 2 minutes later, the hood is closed, and the car was being pulled out. I look at the rep and tell them, "what is going on?" he goes outside, comes back in and says, "well they fixed it". I was like, "really, that was it?" so, the mechanic comes in, and says, "You had a vacuum hose disconnected" I was like "Really?" he says, yeah, and tells me it's a vaccum hose near the engine. I don't know what hose it was, but he connected it and it worked fine. If you know where the vaccum hoses are located near the engine, I would start there.

I followed the lines much like you did and found more or less what you found. I also found out that the black line is the source line that connects to the main vacuum.

I haven't gone back to try to fix mine again yet- that might be today's task.

So far, I found two rotted pieces of line near the vacuum ball under the hood - if you start there, you will see where the black line connets to this bunch of vacuum line.

Once I replaced the rotted line, I still didn't get proper function, but I can now hear another leak behind the center of the dash (where the main plenum is), so I figure I am going to need to take the lower dash back off and partially dismantle the plenum behind there to get to that leak.

The "good" news is that I'm getting real good at taking my lower dash apart! :o)

I'll let you know what I find......

My AC will switch modes as well,but I have a twist to my dillema. My "door open" alarm sounds. Once started I cannot get it to stop. At first I belived it was the door switch but it only happens with the AC running. Ya think it's possessed?

My AC will switch modes as well,but I have a twist to my dillema. My "door open" alarm sounds. Once started I cannot get it to stop. At first I belived it was the door switch but it only happens with the AC running. Ya think it's possessed?


I don't know what to tell you. Sounds to me like there is some kind of short in your wiring, that causes the chime to go off when the A/C is switched on. You may have to take it in to a mechanic who specializes in electronics, and wiring.