On my 2000 mustang, the A/C was blowing warm air, so I bought a bottle of that AC Pro at walmart, followed the instructions exactly and it still blows warm air! WTF? Is the AC compressor supposed to engage and spin constantly or is it supposed to engage/disengage every few seconds? Mine is doing that so I dont know if that's a problem or not. What else would cause it to still blow warm air? I put about half the can in and stopped because the gauge on the can was in the max normal range. Any thoughts?