I did searches on A/C in the forum which got me to this point. I also have a helm manual that I have been using. My AC blows warm air. After going through the helm checklist, it says I have to replace my pressure switch on the compressor.

Here is what happens: I only have a guage for the low side pressure. With the A/C on full blast (engine running) compressor kicks on at about 35PSI, pressure drops to about 10 PSI and the compressor kicks off. If I jump the switch on the accumulator the compressor stays on but the low pressure drops to zero.

The manual says if the compressor cycles feel the inlet and outlet tubes from the evaporator and see if there is a temperature difference. There isn't, they are both warm.

My hunch is that if low pressure drops all the way down when the compressor is running, that there is a blockage on the high pressure side.

Looking for some input. Should I replace the switch and see what happens. I may not have put in all the info that I know....ask any qeustions. I may have missed something.

You must use a guage set with both Hi side and Low side guages to get an accurate reading of whats going on in the system. If high side is high and low side, low, there is blockage in the system. If both sides are low, probably low on refrigerant. Ambient temps and airflow across the condensor affect pressures also. The low side reading is definetely low but this only tells you part of the story. Get a guage set hooked up, read the pressures and let us know. Fred

you may also be low on r134a, which should be expected on a '96. I just recharged my system today:) go to autozone and borrow their gauge set. see if you're in the right range on high and low sides. good luck

Just wanted to let you guys know that adding more 134a took care of my problem. As I was adding it, the compressor stopped cycling and just stayed on....worked out well. Now it is blowing cool....not COLD, but I did test it on the hottest day we have had here in 3 years!

Remember, when adding refrigerant, run a big cooling fan over the condensor, in front of the grill. It makes things more "road like". Do this when testing system w/guages as well. Things get more accurate. Pressures go up as temps go up. Airflow is a "must have" to get the duct temps down where they are supposed to be.

Running cool not cold and stays on with more R-134A. I would bet that your expansion orafice tube is clogged just changed mine, it was nasty.

How cold does it get on Max going down the road at highway speed? Near 40°F?

The bygone days of the GM A-6 compressor are gone! That thing would cool a 1300 Sq. Ft. house! Duct temps of 34 degrees were the norm! No more, with the newer, smaller compressors and the inefficient R-134A. I'm luck to see 40 degrees at the center duct.

Fortunately, my pickup still used the A-6/R12. It'll freeze you out of the cab on a 95 degree day unless you turn it down!

Running cool not cold and stays on with more R-134A. I would bet that your expansion orafice tube is clogged just changed mine, it was nasty.

MDT, did you have to evacuate and recharge the system? Where is the tube that you are referring to?

The tube MTD is referring to is behind the passenger side signal light, its inside the line and can't be seen without breaking the connection. It has a screen that collects junk from the compressor, if it gets clogged you'll loose your efficiency in cooling and possibly blow a hi pressure line. I've had one let go due to clogging up with failing junk from a compressor on the way out.

The tube MTD is referring to is behind the passenger side signal light, its inside the line and can't be seen without breaking the connection. It has a screen that collects junk from the compressor, if it gets clogged you'll loose your efficiency in cooling and possibly blow a hi pressure line. I've had one let go due to clogging up with failing junk from a compressor on the way out.

I had that problem with mine too, I know a big part of it came from using the Leak seal R-134a cans, I over did that a bit.:mad:

You do have to evacuate and recharge the system after orafice change. Good idea to flush as much of the system as possible at the same time.