[NiftySVX]

My guess would be that the system is undercharged, but since it has been retro-hacked there is no way of ever getting the refrigerant charge right. There is some sort of formula that converts R-12 capacities into a reccomended 134a charge amount, which will get the pressures in the system kinda-sorta in the neighborhood of where they should be. If the charge is approximatly correct, then you probably have a problem with one of the sensors in the climate control system, the favorites to fail on these seem to be the evaporator and refrigerant temperature sensors.

Hold the OFF and AUTO buttons and turn the key on, then post the results. Anything other than a display of '00' is abnormal once the test completes if you do it outside in the sun.