Hi Thom, Jim the advice is good except for use of compressed air to pressurize system. Compressed air is full of water unless you're in a very dry part of Texas, water and refrigerant and aluminum parts are a bad mix. Water + refrigerant makes hydrochloric acid which is very unfriendly to the aluminum evaporator and condensor. Better to pressurize the system with a can of refrigerant or use compressed nitrogen. (I realize not everyone has compressed nitrogen in their basement) A quick way to see if there's pressure is to remove the clutch cycling switch from the accumulator. If there's pressure a little bit will escape as you're unscrewing the pressure switch. As further confirmation you can depress the Schrader valve on the accumulator port once the switch is off, taking precaution against getting it in your face. On a warm day with the engine off the pressure in the system should be about 80 psi. If you've got that then the problem is likely electrical, such as the clutch cycling switch , the compressor field coil or the HVAC control panel on the dash