I have a 1990 corsica that has recently had a a/c conversion from r12 to r134a. The air will blow cold but it doesnt blow very strong. Recently, the air has completely stopped blowing. I dont think it has much to do with the a/c itself because the compressor comes on and air still wont blow even if the control is set on vent or heater. Any ideas on what the problem may be?

Welcome Aboard!

Check to see if the air has diverted to the defroster outlets on top of the dash. If so, the likely cause is a lack of vacuum to the HVAC controls. This is usually due to a vacuum line either failing or disconnecting in the engine compartment. There is also a vacuum reservoir (tank) which may be leaking. Once vacuum is restored to the controls, operation should return to normal.