New Hack: Poor Man's Air Conditioner Service
http://www.focushacks.com/index.php?modid=85 If anyone has other tips or corrections, post them here. This is how I've always handled A/C Recharges, but I have no formal training, so this is definitely "shadetree" (a.k.a. do-it-yourselfer) advice.
Answer:
when testing the A/C, have it on recirculate, max fan, max cool. the thing you are calling a collector is the receiver dryer. Low side pressure should be almost exactly the ambient temperature. you really need to moniter the high side pressure too. If the compressor is working properly, you'll see high side pressure rise as low side falls. Then when the clutch unlocks, it will try to equalize. You cant check the evaporator or expansion valve (without dismantling the car) with dye. Only a sniffer works for that There is a metric ass ton of things to know when troubleshooting AC, but this is definatly a good hack and usefull for the masses. I always charge it while it's running and the A/C is cranked to max cool, fan as high as it can get, and recirc on. The reason is that the charge port is on the low pressure side but when the compressor isn't running the pressure is about equal on both high and low side (give or take). So it takes more PSI to fill the system if it's not running. When the compressor is on, the low side has (obviously) lower pressure and it more readily accepts a charge. Just don't over-fill it. It sounds like you're short-cycling and the most common cause is not enough refrigerant.