Gen2 compressor...
Here is a step by step of what I did, most of it was recommended to me by my uncle who is retired bmw master mechanic.
* I replaced my condensor, evaporator, o-rings, and compressor with all new parts from toyota. in addition to the o-rings where the lines connect to the compressor I also used that copper gasket maker stuff too. I was told to use it on the flat metal surfaces that touch the compressor housing, and to NOT let it get on the O-rings when i'm applying it (some will get on them after you tighten them down). Make sure it's a very very thin layer that barely covers the metal surface. Tighten everyting down...
* Use a vacuum pump on the low-pressure side connector (on a USDM car that's the one toward the passenger side of the car). Leave the vacuum pump connected and on for about 20 minutes. Then remove it and connect a A/C pressure guage to the low-pressure port to see how much vacuum you're getting. It should be around 30 psi of vacuum. If it's less, connect the vacuum pump again and let it run, then check the pressure again until you have around 30 psi of vacuum. DO ALL OF THIS WITH THE CAR OFF AND NOT RUNNING.
* Now that you have vacuum'd your system, leave the pressure guage connected to the low-pressure side, and note the exact pressure reading. Leave it connected for about 1.5 - 2 hours (still with the car OFF and NOT running). After about 2 hours check the pressure reading. If the pressure has fallen then you have a leak in your system. If not then you are ready to fill with R12 or R134 (or substitute). If the pressure falls quickly you know you have a big leak and something is probably not connected or seated properly. If the pressure falls slowly then you have a small leak somewhere that is going to be a pain in the *** to track down (but nevertheless needs to be tracked down and fixed, otherwise the system won't hold the gas for very logn and you'll just be wasting money by filling it up).
* If you have good pressure still, and no signs of leaks. Now you're ready to fill the system up with your choice of R12 or R134. If you have a Low/High automobile air conditioner pressure guage set, then connect the HI (red) guage to the high side of your system (the connector on the driver side). If you don't have a pressure guage set, no worries...
* Take your first can of R12/R134, shake it up really good for 30 - 60 seconds. Connect your can of gas and your lines to the LOW PRESSURE side. Start the car and turn the A/C on and all the way to the cold side, and make sure the fan is on high.
* Now if you have some kind of a trigger or valve to open to let the gas flow into the system, now is the time to open it up and let the gas flow. Let the gas flow, while giving the can a good shaking about every 60 seconds. When the can feels empty disconnect the can/lines to the low pressure side. Make sure you disconnect the line first... and then the can (unless you have some sort of an on/off valve, otherwise you'll let air into the system or you'll let gas out). Now shake up the next can, and connect it... etc....
* Keep filling the system until your pressure guage connected to the low side reads around 35 psi (or the high pressure side reads around 140-150 psi). If you do not have a pressure guage set, use the one that came with your cans/filling lines. If they did not come with one either then don't even attempt this until you get at the very least a pressure guage to fit to the low-pressure side.
* So this whole time the car has been on and running, with the A/C on COLD and the fan on HIGH. By the time you get around 35psi of pressure on the low pressure side you should start feeling cold air coming through the vents. If you don't then something is wrong. Make sure the compressor clutch is kicking on when you turn the A/C on. You should hear it click on, or you should see the RPM drop/rise when you turn off/on the A/C. If this is not happening then something is wrong that the compressor clutch is not activating. And that's a whole other can of worms
