Air and road - I just called a welding supply and I can get a tank of nitrogen. I think I will try what you mentioned. Perhaps you could give me a little more direction. Would the procedure be to vacuum the system, put in a pound of refrigerant, and then connect the nitrogen tank to the system, with the compressor running? Or would I shut off the car, and use the tank pressure to get it higher? It sounds like the idea is to use a little refrigerant, and the nitrogen is to dry and pressurize the system? I don't think the sniffer can sense nitrogen, right?