[jon75]

When installing a new compressor, you should pay attention to how much oil is required for the system. R134a systems use PAG oil. It's quite cheap and I recommend taking an extra moment to ensure you have the correct amount in the system.

Prior to installing the compressor, remove any plugs that are sealing up the port holes and dump out all of the oil that was in the compressor out into a container. Check the labels on your truck to see how much oil the system calls for, and add that amount into the compressor ports before installing. Next, install the compressor. Be sure that you replace EVERY SINGLE O-RING with O-rings that are rated for R134a. They are usually green and a kit for that is around $4 at O'Reilly's or NAPA. After you have finished replacing the O-rings, filter/drier, and anything else, install the quick connects for the R134a onto the R12 ports on your system, paying close attention to the difference between high and low side (high side is post compressor, pre-evaporator). Once you have installed the ports, put a vacuum on the system of 30 inches. It should hold the vacuum for 5 minutes without falling below 29 inches. If it does, you have a leak in the system (most leaks will be evident right away and you won't have to wait that long to see the vacuum drop).

Once you have verified that you do not have any leaks, NOW you can charge the system. The system will take the first pound or so very quickly, since it is still under vacuum. Make sure that you use a gentle rocking motion on the can as you are filling the system. Be sure to measure out with different can sizes how much you need to fill the truck with. It is best to go under the allowable amount rather than over. For instance, if you need 2.2 lbs but you can only find 2-16 oz cans, just go with that. You will have nice cold air and your system won't be stressed. DON"T PUT IN TOO MUCH!! After you have gotten most of the refrigerant into the truck, it may not take the last little bit very easily. If this happens, start the car and run it on MAX a/c with all windows up and the driver window down 2 inches. If it does not take the last bit as the vehicle is running, turn the can upside down and gently rock from 10 o'clock to 2 o'clock positions until all the refrigerant is out.

Once you have charged the system, make sure that the compressor clutch is cycling on and off correctly (which should happen immediately after you start charging the system), you don't hear any odd hissing noises from any lines, and that the air inside the truck feels nice and cool.

I hope this helps you out. This is the system I have adopted from working out of my garage fixing A/C systems without the use of a $5000 machine. All I have is an air run vacuum, a/c manifold gauge set, and the refrigerant cans. I have not had one single complaint and I am EPA and ASE certified in A/C and heating systems. Good luck!