P/A Guy #1

I would appreciate some knowledgeable help so that I don't make my air conditioning worse than it already is.
Typical situation-A/C does not blow cold. Worked like a champ maybe two-three years ago-but doesn't work now. No problem for me-that's why the top comes off and the windows roll down. My Wife disagrees with this strategy vigorously.
I have a manifold gage kit and have used it before. I also have the shop manuals. The shop manuals have a great deal of valuable information but are somewhat difficult to navigate.
Threw the gages on-had 30 psi static pressure on both high and low pressure sides. There is a lot of information on the Internet-it seems as though 40-50 psi is the typical advised range.
When I start the car and turn on the A/C, the clutch engages and stays engaged and the compressor pumps. However, the low pressure side stays at about 30 psi while the high pressure side rises to around 100 psi. The line around the low pressure tap gets warm. The line around the high pressure tap gets rather hot. Threading through the shop manual, at this point it pronounces my compressor DOA.
Here's my question: Since I have a variable displacement compressor, is my charge level so darned low that it doesn't have the capability to pump up? I'm familiar with a fixed output compressor, where if functional, it draws down the low pressure side, elevates the high pressure side, and if the low pressure side drops sufficiently low, causes the clutch to cycle.
I just don't want to overcharge the system and 30 psi inlet is about where this pressure should be.
So-what impact does low (as I've been led to believe) static system pressure have on variable displacement compressor operation and system performance?

Thanks!

BigGun

Low pressure in a C5 is usually indicated by a cool passenger side and warm driver side. If it gets much lower than that the compressor will cycle off. Are you getting any cooling at all?

gimp

Hold on - have you first tried an AC charge (or, to do it right, an evac and recharge)? You can pay a shop to do it, or you can do it and if it ain't right you can pay a shop to evac it.

Your symptoms are similar to those of simply not having a lot of refrigerant. And it's a cheap thing to try.

Bill Curlee

Your pressures are all out of whack.. Try recharging to the proper specs. If your not confident of the condition of the charge, install a new orifice tube and receiver dryer and then fully recharge.

I also recommend adding an oil charge to the mix.

gimp

Would you make that UV oil, Bill? Doesn't cost much more, but it'll let OP know if he's leaking.

Bill Curlee

Sure,, but then you would need a black light to see it. I have a halyon detector so, I often forget about the dye.. Good recommendation..

BC

gimp

Yeah, I figure a ten dollar UV flashlight is cheaper (and has more applications - halloween, parties, jokes about bodily fluids you can see fluoresce under black light) than an electronic refrigerant detector.

Fast one

Last week I did the same thing Bill suggested to my '98 and added 2 oz of oil to the system, after the vacuum was removed it took three hours to add 26 oz of refrigerant with the engine idling. The system is back to normal with cold air and the high pressure side reads up to 350 PSI like it used to a few years ago. I had to buy a cheap O-ring kit at Autozone because the ones that came with the receiver dryer were too thin and the orifice tube didn't include one for the line, both were GM parts. I tried to reuse the original O-rings but the system wouldn't hold a vacuum until the new O-rings were installed. The cheap $3 orifice tube type was installed, not the more expensive variable type.