2000 Cavalier. I have an interesting problem with my A/C system. Just over a year ago, I replaced the compressor (front seal leak), the orifice tube, the accumulator, and the main A/C line assembly (leak at the high side port). Everything has been working fine since... until a month ago. I noticed that when I come to a stop, the system starts blowing warm air. When I pull away from the stop, it starts blowing cold again. When it's blowing warm air, I can hear the compressor cycle on and off quickly (few seconds). The when the compressor comes on, I can tell the engine really takes a hit from the extra load. In a few instances, it has even killed the engine. I also noticed that the A/C belt would be less than stable. It would wobble quite a bit. Then I noticed that the radiator fan wasn't working. Ah, that could be why it's blowing warm air at a stop. Took the fan motor out, banged it on the ground, wired it to the battery and it started working. Took the motor apart and cleaned it really good (didn't seem that dirty inside), put it back together and it works great. When the A/C switch is on, the fan comes on. A/C still had same problem though. I took the car up to my buddy at Autozone discuss the problem with him and let him see what it was doing. He suggested that the high side pressure might be too high. He suggested that I replace the high pressure switch. Right after that, while we still had our heads under the hood, I noticed dye coming out from the ports (maybe just one) of the compressor and leaking onto the ground. Now we were thinking that maybe the compressor was having some kind of internal problem. We decided that since the compressor, accumulator and orifice tube were still under warranty, I might as well replace them. So I did. Charged the system, 'by the book', with the vacuum pump and real manifold gauges. Everything looked fine and it was running at about 45F when it was about 90F outside. "Job well done," I thought. About the time I disconnect the hoses, something happened and it started blowing slightly warmer. Just a fluke... I hoped. After driving it for a couple of weeks, it's now doing exactly what it did before I replaced all those parts. Really bogging the engine down; blowing warm air when at an idle; belt shaking... when I pull away from the curb, it blows nice and cold... if I stop, I get warm air. It must be the high pressure switch that causing all these headaches. Last night I replaced it (without having to discharge the system). Started the engine and everything seemed fine again. At first the belt would wobble but eventually it settled down. The compressor wasn't fast cycling like it used to. I thought I had it fixed. After a few more minutes of running it, however, the same problem returned. I changed the select knob from recirculate to dash vents and turned off the A/C button. The compressor disengaged. I then turned on the compressor button. It stalled the engine. Started up and took it for a drive. Nice and cold air (just under 50F, 90F ambient). When I stopped, it started blowing warm air and fogged up my thermometer. What is going on? Please, can someone answer this mystery for me? New compressor (which includes the low pressure switch, right?), new accumulator, new A/C line assembly, new orifice tube. I have a theory as to what I think it might be now, but I want to see if any of you experts have that same theory before I mention it. Thanks in advance for any advice you can give.

Lonnie.

Hey bro what you have going on is your AC system pressure is low and your system needs recharging. More than likely you still have a small leak somewhere and your refridgerant is low. I promise go grab a can of it and charge your system up, I guarentee your problem goes away..... been there too many times lol

Thanks for the response Tha Dyce. However, I don't see how the problem could be low pressure/low refrigerant. The newly replaced system is doing exactly the same thing that the old compressor, accumulator and orifice tube did. To replace those parts, I had to completely evacuate and recharge the system. When I recharged the system, I pulled a vacuum for 45 minutes on the system. I then let it sit for another 45 minutes to be sure that the system didn't have any leaks. I then recharged the system, taking into consideration the ambient temperature vs low-side pressure (psi) relationship. Also, the compressor still cycles on and off. I've always been under the impression that if the pressure was low, the compressor wouldn't engage. That's the purpose of the low pressure switch. Furthermore, in my original post, I mentioned that we could see dye coming out of the ports at the compressor. I'm thinking this would be an indication of an excess of pressure (high pressure condition). It wasn't because of faulty o-rings. Any other suggestions? Thanks.

Lonnie.

I would check the radiator fan and check that it is clean in between the radiator and the condenser because it sounds like the A/C pressure is going to high when sitting still .

Thanks Tech97. As I mentioned in my original post, the radiator fan wasn't working but now it is; same AC symptoms however. One thing I didn't mention in my post was that after I finished the AC job, I took the car to the DIY car wash and cleaned everything under the hood, including the condenser. I'm pretty sure it's clean, but I'll check it. Here's a silly thought that I had... I was wondering if it would be possible that, while I was messing with the fan motor if it could have been connected backwards. Is the fan supposed to pull air through the condenser and then the radiator or blow air through the radiator and then the condenser? If the fan were spinning backwards, that would explain why I get warm air when I'm at an idle. I'm hoping that's all my problem is, but I seriously doubt it. I don't think the fan motor can be connected backwards. I don't know which way it's spinning right now, though. I'm at work and the car isn't here.

The radiator fan should be blowing air at the engine pulling it though the a/c and radiator and it does need to blow a lot of air to keep the a/c condenser cool .

Have you checked the fan relay switch if not take the relay switch out and shake it and if it rattles then it is bad if not then check for a short in the wires , mine did that for relay switch when I pressed the ac on the fan would not come on then I checked to relay and it was bad the fireing pin inside the relay switch broke off then got a new one and bam the fan came on when pressed the ac on

This little bastard probably went bad.


It is the heater control valve, and should redirect coolant flow when the AC is on to limit coolant flow to the heater core.

It is a passive valve so it never fully cuts flow, but if yours is bad it would cause this issue. Your Water pump could also be failing, and causing this....but you car should run hot at idle if that is the case.





PRND321 Till I DIE
Old Motor: 160whp & 152ft/lbs, 1/4 Mile 15.4 @88.2
M45 + LD9 + 4T40-E, GO GO GO

I'll have to check on the heater control valve. Where is it located? Under the hood or dash? Funny you should mention the water pump though. I have noticed that over the course of the last couple of months that I've been having to add coolant to the system. I don't see any visible leaks to I don't know where it's going. Over the weekend, I drove it once. It took a while for the AC to start blowing noticeably colder while driving. Eventually it got down to 50F. As soon as I rolled up to a stop sign, the temperature started to climb as much as 11 degrees for a simple stop and go. Once I started moving, it would get back down to 50F. Water temperature seemed to be normal... it would stay right around 195F, sometimes lower... so it looks like the thermostat is also working.

Have you checked if the A/C system is low and have you tried using a water hose to cool down the A/C condenser to see if that is the problem ?

I don't think it's low on pressure because I just replaced the compress, orifice tube, and accumulator and then charged it. It still blows cold when moving. Compressor kicks on and off like it should. I had forgotten about using a hose as a method to test the condenser. I was about to use a box fan to simulate driving to see if that made a difference. I haven't done it yet. I'll let y'all know what I find out. Thanks.

Lonnie.

in the engine bay., next to the exhaust manifold or header.




PRND321 Till I DIE
Old Motor: 160whp & 152ft/lbs, 1/4 Mile 15.4 @88.2
M45 + LD9 + 4T40-E, GO GO GO