02 Merc Cougar A/C not working

2002 Cougar 2.5L 130K miles - Decided to check A/C op's even though it's still Spring. Nothing but outside temp air blowing and Compressor Clutch not energizing with Max A/C switch on. Injected R134 at Low Pressure valve until I began to hear the Clutch engage. Clutch now cycling on for approx. 15 seconds and back off for 15 seconds. The Pipe going to the Evaporator from the firewall, behind the dash, is very cold and the pipe exiting is warm, but still no cold air coming out of the (4) Dash Vents. With that I would think there is Cold Air in the Evaporator, Right? Thanks in advance for ideas!