Todd my guess is the low pressure switch, they are prone to fail and leak through the diaphram. If you need any parts or want to convert to r134a let me know, George Martz/Thermal Solutions (Apologies to UUC digest subscribers - posted this there too) On my lunch run (temp=93) noticed some "smoke" coming from around front right wheel, engine temp ok, so popped hood and the AC sytem was spewing all over the inside of right front fender. Coming from the top of the black canister with the sight glass, opposite from where hose enters (yes, I am a complete AC ignoramus, but have a feeling I am about to become much more knowledgeable). Anyone want to give me the bad news - what's going on - did I pop a burst disc or something? Thanks.