A/c Warm Air

[Graya25]

As it has been hot and humid lately, I wanted to use the A/C on my '97 Sierra. No dice, just warm air, as if the heater was on. I bought one of those R-134a cans with the gauge and my refrigerant level was at ~45psi, so the system is properly charged. When I turn the A/C on from the dash, I can hear the roar of the compressor, but no cooling takes place, so I believe it to be working. The clutch plate on the compressor will spin up every couple of seconds, then stop, though this may be normal operation. I also replaced the A/C-Heater fuse, nothing still...

 

Any ideas of what the problem could be?

[bronyaur]

Well, assuming that the A/C is working correctly, the problem could be that the blend door is not functioning. I would start there. I've heard of the problem but never had to fix it myself so I won't be much help.

[Graya25]

After going through just about everything else, it seems like the blend doors are stuck. Does anyone know how to check these out?

[eddinger]

I am new at this but I had thought that mine was full as well, but as it turned out it wasn't. You said that the compressor was turning on and off, did you notice what the gauge was reading at both times? That was my problem. When the compressor was off it read full, but whent the compressor kicked on the dial droped below 25. It was turning on and off because there wasn't enough freon, it has a sfety to keep it from burning up. Maybe thats it, or maybe its the other problem, good luck

[Graya25]

The clutch turns on at 45 psi and drops the pressure just below 15 psi according to my gauge. The pressure then rebuilds and the cycle continues. Is this a sign of low freon? Or is it the blend door?

[eddinger]

if it drops to 15 it must be low on freon. Did you put any in yet? Once you get enough in ther the clutch should run continuously. But don't overfill it. Only get a reading when the clutch is running or it won't be accurate.

[Graya25]

I put a very small amount in, but I got worried that I was overfilling it. After I filled it slightly, the pressure would build to about 50psi (too high), but when the clutch ran, it would drop back down to under 15 psi, at which point the clutch turned off and the pressure built back up to 50psi.

[eddinger]

mine went over 60 until the compressor didn't stop. I started from empty so I knew that I needed over 3 15oz cans to fill mine. That helped alot, I was worried too when I first did it. If you're still unsure of what I'm saying go ask a mechanic you know. I'm sure that they'll give you some free advice. I had converted from R12, had all the old pulled out. It called for 4.25lbs. R12, so 80-85% of that was about 3.63- 3.85 15oz cans.

[Black02Silverado]

It is my understanding that you have to service your system with the compressor turning. If you read the gauge with it not running it will read high. The proper pressure is read as the compressor is running.

 

I never did my truck but that is how I filled my 91 Jetta. I put the gage on it and it was low as the system was running. I only needed to add one can of freon to get my system down to a nice cold air flow out the vents.

 

Stuck air control doors is another issue if your doors are operated by vacuum there might be a leak and they might not be getting any vacuum to open them. Not sure how yours operates.

[radiator]

Feel the two lines attached to the compressor. One should be hot and one should be very cold. This will tell you if the system is working properly. Im not an expert but this is how i was tought how to tell.