I checked the pressure on what I think was the low pressure side (next to the drivers side shock tower) and it was 110 psi, but the car was still hot from driving. I also realized that the fittings are different, the one on the front passenger side of the car has a larger fitting. When the A/C is on it gets only moderately cool, it doesn't get cold. If there are any HVAC people out there, your help is needed.
really you should check the high and low side at the same time. with the compressor on the high side should be around 135(maybe a guy with more mustang experience can correct) and the low side i like to see in the 30-40 range and it should not rapidly drop off. also check for rapid needle fluctuations as this could indicate a sticking expansion valve. have you evac the system and measured the refrigerant yet?
-No I don't know **** about A/C, I have two guages, but they both have the same fitting on the end, so I can't check both sides at once, actually I cant even check one side at all
-Is the fitting on the line coming from the condensor (this is the heat exchanger in front of the radiator correct?) the high or lower pressure side?
-If the fittings are different do I have R12 or is this not true?
-I don't have any means of evacuating the system
-The back of the guage say for ambient of 100F use 45-55 psi so I was thinking 50 should be fine on the low pressure side
you can charge the system with only one fitting, but i would advise against diag with only the high side. if the fittings are the same size then it is an r-12 system. if you have two diff size fittings denoted by red and blue caps(generally) then it is r-134a. until you can get a set of guages that have both sides, use the low side for readings. you should watch for a rapid decline in pressure when the compressor cylces on, the low side pressure should drop and stabilize, if it does not stabilize and continues to drop until the compressor cycles off rather quickly(about ten seconds) then you most likely have a low charge.
In order to properly recharge an AC system, you really need 3 things, cans of refrigerant, gauge cluster, and a vacuum pump.
1. With your car off, hook up your gauge cluster. On one side of the gauge cluster there should be an extra fitting and the gauge may even read vacuum too. Hook up your vacuum pump there and let it run for 1/2 hour or so (grab a sandwich, beer, "quickie", or whatever)
2. Close valve to vacuum pump, then shut off the pump and remove it.
3. Start car, put AC on max (don't worry about killing your compressor, the pressure switch won't turn it on until there is refrigerant in the system) attach a can of refregerant to the low pressure side of the gauge cluster (you may want to purge some of the refrigerant to clear any air out of the lines). Then open the valve so that the refrigerant gets sucked into the system. As you fill your system, the refrigerant will take longer to get sucked up. You will probably have to warm the can with your hands (heat of vaporization) and shake it alot.
4. The number of cans of refrigerant you buy will be based on the volume of your AC system (see your manual). There should be pressure ranges that you will want to fill to based on your manual as well.
5. Close valves on gauge cluster, remove fittings, and give it a test drive and enjoy your cooler car.
Follow up:
I checked the low pressure side, the compressor would kick on and the off about every 5-10 seconds showing pressure ranging from 90psi down to <20psi I put a 12 oz can of 134a in and the pressure steadied out to about 35psi and the compressor now stays on. It gets relatively cold now, however I am going to put in another can to see if I can get the pressure up around 50 psi. I also bought the refrigerant with the dye and plan on getting the uv light sometime in the near future. So if I have any leaks I will be consulting you people again. Thanks again for the help