I have an 84 300d and the ac will not blow cold through the vents,only blows really hot air, the compressor is working and so is the aux fan and the lines are getting cold, ac compressor comes on with the dial is turned on heat or cold and buttons turned on vents or floor. Compressor only turns off when it's on the ec button or climate control is turned off completely, I checked the mono valve and seems to be stuck and the seal is really torn , maybe a possible cause?