I just bought the 2 way R-134a retro fit& charging kit. It came with r134a oil and Refrigerent. 2 Cans of 134-a and I got it at pep boys. All it says is have it emptied, I did THen it says screw the r-134a adapters that are coated on each of the service ports. I only can find one service port on the reciever/dryer. I had the AC unit replaced a few years back and got a new dryer and compressor. I am sure it was r-12 because it was only 3 years ago. Where is the low pressure service port. my hayes and chiltons do not have any pictures of it. Also how long does it take a can to empty into the system? It says nothing about schrader valves. I do know I got new ones when they redid the system 3 years ago. Is it really that simple?

i have one myself... if u got a O.E replacement one.... and never filled it up... u can just put the new fittings on and then charge away... u said u have it drained.... then yea just put the new fittings on and like charge away....the only problem u would of had is if u had some r-12 in the system already.... there should be something in the box about putting the fittings on... and about the other port... i have no idea....sorry i cant help u with that u find it please post it i plan to do mine soon i have the box in the garage... thanks `

the LOW pressure port is on the side of the accumulator (receiver/drier) the high pressure port is on the line down beside the engine on the passenger side, it should be real close the the frame rail towards the front of the engine. DO NOT hook up to the high pressure port. connect the hose to the LOW pressure port on the accumulator and start the car, with the car running and the A/C system turned on to high start filling the system with the oil charge can first, then continue with the other cans of 134A.

P.S. if you have not already started filling the system I would urge you to rethink the 134A, it may be worth the xtra money to put the 12 back in the system. I did the retrofit on my car and I HATE it. do a search and you will see Vader mentioned something about another type of stuff called 414B (hot-shot) that is supposed to be cheaper than 12 but more efficient.

The low side service port is the one that is on the accumulator. It will have a blue cap.

The high side service port (red cap) is on the liquid line that runs along the frame rail underneath the coolant bottle. It will be a 3/8 fitting most likely.(GM used a 3/8 high side service port on most vehicles, I guess to keep people from hooking up the hoses incorrectly) you may have to buy a separate high side service port specifically for GM products.

I would strongly recommend replacing the accumulator, orifice tube and back flushing the system (not the compressor) with a/c solvent or at least with ester oil.

The accumulator holds about 2 ozs of mineral oil and mineral oil isn't compatible with R-134a.

The evaporator and condenser cores hold about 4 more ounces of oil.

For best results, you should have the system evacuated for at least 15 minutes, preferrably 30-45 minutes, but 15 will do.

Then, follow the instructions given with your kit (most likely your kit only came with one hose).

Keep the can upright, so gas is allowed to enter the system, it will take its time about going from the can into the a/c system.

WARNING: DANGER WILL ROBINSON
If you turn the can upside down, liquid refridgerant will enter the system, and you may damage your compressor, because you can't compress liquid. POP goes the compressor.

If you want to speed up the process, set the can on or near the heater hoses or radiator hose or on the intake manifold, and every now and then pick it up and swirl it around a little bit. This will increase the can pressure. DO NOT USE FLAMES TO HEAT THE CAN. the can will become noticably warmer when it is empty.

One adjustment you may want to make is on the a/c cycling switch that is screwed onto the other port on the accumulator. After charging the system, if it doesn't seem to be cooling down enough, try turning the adjusting screw counter clock wise, no more than 1/4 turn. (R-134a operates at higher pressures than R-12, and adjusting the switch will allow the compressor to operate longer before cycling off)

Lastly, you mentioned schrader valves, the low side port probably has its own valve and you will need to remove the schrader from the accumulator. The high side will probably use the existing schrader valve.

I have used "probably" and other qualifiers, because I have not seen your a/c system or retro fit kit, and with out knowing exactly what you have, I can only give general advice.

Good luck and yes it is that easy. The hard part is figuring out why the a/c doesn't work at all.