tpnotch420

92 SC400 my blower motor seems to be stuck on low. I have checked both the resistor and the power transistor and both checked out good per my service manual. I ran the Cliamte control diagnostics and came up with pressure switch problem. I'm pretty sure it'slow on freon. So when I try to add freon the gages indicate it's full so I think there is air in the line. From my research I've concluded that I probably need to get a vacuum pump to remove the air before I can refill it but I'm not sure.If there is another less expensive way to fix that I'm all ears as cash is tight right now. On the blower motor speeds I can't seem to find anything else that could be causing the problem. Is it possible that the low freon is causing this not to function as well or do I have a problem with my ECU?

Sorry I forgot tomention that this system has been converted to134a before I got it and the ac worked fine for the last 3 or 4 summers

Any help would be appreciated