95 Sierra AC Problems

The AC in my 95 doesn't want to work correctly. It has plenty of coolant in it. When I start the truck and hit the AC button nothing happens. If I rev the truck up to 3500-4000 RPM, the compressor kicks on and will freezs you out of the truck for a while, but it never cycles. If you turn the switch off and then back on again, the compressor again wont come on until the engine is reved. It works great if I'm towing because the truck is running at higher RPM. I have replaced the cycle switches and am wondering if I need to replace the compressor as well. I had the blower resistor replaced this winter when I only had heat on high, so I don't think it has anything to do with that. With summer coming to an end, it isn't THAT major of a concern, but I would like to get it working properly. The truck has 407,000 miles on it and has never let me down. Engine is original and has not been touched, but has had a couple of trannys. A FAR better vehicle than the wife's 98 Windstar.

I'd be curious of the clutch assembly on your compressor. Remove all of the electrical connectors (i believe there is just 2) on your compressor and make sure they are making a good clean connection. If that doesn't cure the problem then it is possible that your strainer in your A/C System is clogged and needs to be replaced. When the strainer gets clogged it causes enough pressure on the A/C System and the Compressor won't kick on.

What do you mean by strainer? Where is it located?

Unfortunately, you can not see or change the strainer yourself. It's located within the Freon lines and is usually under the dash in the HVAC System. It's usually an A/C service man call or service center of some kind. Sorry :(

Sorry I kept calling it a "Strainer" it's actually called a Drier. Interesting article about everything A/C Related here.
http://www.aircoparts.com/INFO/DRYER.htm