Upon start up the AC compressor has siezed (or it's pulley) and the serpintine belt just SLIPS over the pulley generating a horrid screaming sound.... (both plugs going into the compressor have been pulled so there is no command for AC)

What do I do?

Normally on any other part I'd pull it and try to repair/replace the obvious, but you cant remove the AC compressor due to those high pressure lines.....

What should I do?

Replace it. The compressor more than likely locked due to crap on the orifice. The orifice is on the bottom line at the condensor connections.

If you have any A/c service lines, hook them up and dump the gas into a gallon of water. It will enable you to remove the high pressure lines.

hmmm greek to me....Ill go take a closer look at the compressor.

What are AC service lines? Where do those hook up?

Only the clutch engaged wheel should have failed. Disconnect the wires going to the compressor, and then the wheel on the compressor should just spin freely.

ok upon closer inspection, I see a single service port on the high pressure line bracket that looks like a quick disconnect air fitting....

I aslo see where the 2 high pressure lines connect to a bracket that bolts to the AC compressor, but you said something about the pump locking up because the lower line was occluded?

You put them on the fittings. The low pressure is brfore the compressor and after the accumulator. the high pressure is directly after the compressor. for $20 you can get a functioning set with gauges.
PS if you don't have r134a now is the time to upgrade, there's a fitting kit to upgrade to r134a from r 12.

The orifice is in front of the truck. You have to take out the passengerside lower lens and behind it is two a/c lines and fittings, the lower one has an orifice valve that catches all the crud off the bottom. You have to remove it, blow the system out and then flush it if you can before installing a parts.

Only the clutch engaged wheel should have failed. Disconnect the wires going to the compressor, and then the wheel on the compressor should just spin freely.
did that long ago when it started acting up....now the whole sucker is locked up tight like a 18 year old church goer wearing a chastity belt....

You put them on the fittings. The low pressure is brfore the compressor and after the accumulator. the high pressure is directly after the compressor. for $20 you can get a functioning set with gauges.
PS if you don't have r134a now is the time to upgrade, there's a fitting kit to upgrade to r134a from r 12.
there's only one fitting that I can see :( I assume those are two types of coolant? While I know a small amount on IC engines, I know absolutely nothing about how AC compressors work...lol Why would you need a fitting kit to change to a different type of coolant?

Well, it's all about money.
the laws changed a few years back making r 12 obsolete and now it's a simple matter of economics to use R134a vs R12. The fittings are different to keep it from being easy to mix gasses.

Did you say you have the quick release type? that sounds like r 143a.

After going to www.howstuffworks.com (http://www.howstuffworks.com/) I think Im up to speed now on the AC system's function.

What is the silver cylinder that's behind the turbo on the low pressure line before the low pressure line gets to the compressor?

And where is the expansion valve, in the cab somwhere?

With you pulling you wires/plugs off your compressor and it's still locked up, sounds like you have a seized clutch. If that's the case you will have to remove the entire compressor unit. All your 134a will need to be evacuated as QM stated. So when you repair/replace your compressor, unless you have or know someone with an a/c vacuum pump, you'll have to take it in to get leak checked and pumped out. If I remember right they draw about a 40kpa vacuum on the system and let it sit. If the system starts to vent up, you have a leak. If it maintains a vacuum, they will refill the system, but it must have a vacuum before a refill or your a/c will over pressureize which could lead to severe damage if your over pressure sensor is faulty. It's been awhile since I've dealt with vehicle a/c systems so I hope I'm not feeding incorrect info. Can someone verify this?

The accumulator, receiver/dryer and filter all in that silver can.

If you buy all three, the compressor, accululator, and orifice, the parts store will give you 12 months on the compressor. whoop te do. but all three should be replaced ideally.

I did sucessfully pull 30 psi vac on the a/c system in my truck with the stock vac pump hooked to the a/c service lines after I blew compressed air through the condensor to dislodge the bottom oil.

Typo on my part. It should be 40 hg/in not 40 kpa. So many ways to read vacuum/pressure (torr, Hg/in, psi, etc.)

I had that happen on my truck, and the dealer removed the clutch assembly and reinstalled the pulley and I was on my way. Temp fix as the compressor was out of stock.

Can you install just a new clutch and bearing on the old compressor? There's a kit on wwwrockauto.com for ~$100. You'd still have to flush the system and change the orifice.

You should be able to just replace the clutch, but i'm not sure if you can do it with the compressor installed. I havn't had mine apart, but from what it looks like the front plate can be unbolted and removed with the clutch and bearing. Sometimes it's not even the clutch and the solenoid that actuates the clutch is shot; they're generally easy to repair. I don't have the GM manuals, but for those that do, it might have a breakout diagram of the compressor. For safety reasons, I would go ahead and purge the fluid and remove the compressor. From there you can work on your bench.

I think there is a tool for the clutch removal but can be done on the truck easy enough if thats the only problem.

And doesn't require changing the coolant either.

If a clogged orafice is the problem you'll hear that new clutch locking up. If you change the orifice and flush it at that point you're good to go.

Also, When my clutch seized the crank pulley boke too. It's just uerathane sanwiched between two cast steel rings, it can't take the torque.

True but i was only addressing that the pulley bearing and clutch had locked up. I am not aware of any oriface clogging causing this BUT by all means everything should be checked and taken into consideration before starting any work.

Here is a good article on do it yourself A/C. So far I have done everything according to the article. Only problem is, I could not find a shop around here that rents the equipment to draw a vacuum on the system and recharge. I will have to have Midas do it for about $150.

http://www.diynet.com/diy/ab_auto_air_conditioning/article/0,2021,DIY_13674_2276708,00.html

You might be able to take it to a small, privately owned, repair shop and get a better deal. I have one down the road and since I too am without the pump, they only charged me around $80.