Yukulele - from your posting it sounds like you have a Harrison HT6 compressor (also known as the "belly leaker"). I have a 97 Tahoe with the same set up. They are well known to leak because of flawed design.
Your best bet is to replace the compressor, orifice tube, and accumulator. Then have it professionally evacuated and recharged.
Should run you about $400 for parts plus evac and recharge fees at your local AC shop. I did all this to mine and it blows nice and cold now.
Good luck with your Yuk' and let us know how you fixed it.
As was said.
Also the stock HT6 is also known for Black Death
http://www.ackits.com/c/BlackDeath/Auto+AC+Compressor+Failure+(Black+Death).html, meaning their garbage and when they start to go they contaminate the entire system with black sooty crap.
I recovered the refrigerent and pulled my system appart due to a leaky schrader valve, while I was at it I replaced the orfice tube and noticed the old one was starting to get black, so next year I will buying a brand new Sanden or Seltek compressor kit and completely flushing the entire system and replacing anything that looks bad.
Also was told that insulating the suction line from the accumulater to the compressor and the entire rear suction line, not the liquid line, helps greatly reduce the amount of superheat the compressor has to deal with, which inturn keeps subcooling temps down in the liquid line which helps to lower evaperator temps in the dead heat of summer
Also when you guys charge your systems, the charge amounts on the accumulater are actually out dated, both the Burb and Hoe should be charged with 64oz of R134A. I also beleive the Burb take 11 oz oil and the Hoe takes 9 oz this is if your system is clean and dry.The guys at AC KITS had told me this.
If anyone plans to flush yourself, you need to remove evey componet and flush them seperatly, and that means removing the rear evaperator and expansion valve. It's almost impossible to flush the condenser as the condenser is a parallel flow conderser, meaning if you blow it in one side it dosn't mean you cleaned every coil inside, (think your radiator). Anyway good luck guys, it's tough to do it right without the proper equipment, somtimes it's best left to the pros.
Check out this place too, pretty awsome prices and stuff here.
http://www.ackits.com/merchant.mvc?Screen=CTGY&Store_Code=01&Category_Code=Chevrolet99tahoe5-7
