The AC on my 1999 GP SE 3.8 is running a bit warm. Not terrible, but it looked simple enough to add a bit of coolant to chill it out a bit. I bought a 13 oz can of Quest High Mileage R-134a forit . I got it home and following instructions both on the can and a website I found here, I tried to recharge my AC. The gauge on the hose sits steady at about 23-25 pounds until I start opening the valve, then jumps well into the red zone. I don't here anything flowing, and when I close the valve, remove and reattach the hose, the pressure is the same. The instructions I have say to keep the can upright, but to do this I have to hold the can quite a way above the low side valve on the firewall. The AC is on max and the fan on high while I'm attempting this. Any ideas on why I may be having this issue with what SHOULD be a simple repair?

Welcome to AF!! Are you sure that the system isn't overcharged to begin with. An overcharged system will not work properly just like an under charged one. Also make sure that the hose is properly seated on the low pressure connector before opening the can. If it isn't tight enough or if the hose does not enter the port far enough it will hold all the pressure inside the can thus the high reading.

The gauge on the hose sits steady at about 23-25 pounds until I start opening the valve, then jumps well into the red zone. I don't here anything flowing, and when I close the valve, remove and reattach the hose, the pressure is the same. The instructions I have say to keep the can upright,

I recently had a spat with my a/c as well. I did mine later at night and may have screwed my compressor up. The can I have explicitly says, "HOLD UPSIDE-DOWN". These small cans are meant for use on the low side service port for vapor charging which is why you hold it upside down. They typically have a tube inside that goes most of the way down (at least on larger 20/30lb cans) and by law can only be filled 80% VOC. with that you can liquid and vapor charge, unfortunately az gage manifolds only allow for vapor charging. if you ran your a/c for a good bit after liquid charging your low side you may have ruined your compressor due to slugging or the compressor trying to compress liquid. Im gonna check through all the related fuses and then if that fails and probably just buy a used compressor.

I also did some reading as I found it peculiar that people were having trouble buying R-134a refrigerant. EPA regulates it and on their site it says that anyone can buy this particular refrigerant. Although seemingly outdated:

"Sales Restrictions
Right now, there is no restriction on the sale of HFC-134a, so anyone may purchase it. This year, EPA will issue a proposed rule under section 608 of the Act that will include a proposal to restrict the sale of HFC-134a so that only technicians certified under sections 608 and 609 may purchase it. After the proposed rule is published, EPA will review comments from the public on the proposal and will then publish a final rule sometime in 1998 or 1999."

- obviously its still for sale publically as it is on all az/walmart shelves Ive seen. Maybe if someone asked for "freon" at az or walmart they would be told they are unable to sell it to unauthorized persons because it is in reference to cfc-12, not hfc-134a.

Well, as of this morning the AC is still running, so I don't think I tanked my compressor (thank GOD!) and my can said to hold it upright to vapor charge, so I think I got that right (I'll have to reread the can again to be 100% sure). My gauge only showed about 25 psi when I put it on before peircing the can, so I don't think I'm overcharged. I guess I'll just have to keep fiddling with it, and do some more research.

One more quick question. How long should it take for a 13 oz. can to empty?

anyone? I hate to nag, but I'm concerned about this.

goaliegod, I hope someone is still monitoring this thread. I have a 1999 GP SE, and I cannot locate the low side schrader valve in order to charge my ac. Some people say its next to the firewall, some say its under the air intake box (where the air filter goes) and still some say its the valve next to the air intake box. Is there anybody monitoring this thread that can answer my question? I hate to start a new thread about this since this thread exists.

goaliegod, I hope someone is still monitoring this thread. I have a 1999 GP SE, and I cannot locate the low side schrader valve in order to charge my ac. Some people say its next to the firewall, some say its under the air intake box (where the air filter goes) and still some say its the valve next to the air intake box. Is there anybody monitoring this thread that can answer my question? I hate to start a new thread about this since this thread exists.

At times it is better to start a new thread on your problem due to the variations in Grand Prix models. What engine does your SE have?

If you have a 3.1 the low pressure port (service port) is a different location than the 3800 which is at the firewall. So if it is not by the firewall then look for a blue cap around the area of the A/C compressor on the lines.

My 99 SE has the 3100. I need to know exactly where the low valve is located. The only valve is see is the one just to the side of the air breather box.