Before you change out the pressure switch check to see if the pressure is getting high enough to pull the fan switch in. Do you have a/c gauges. I think the pressure has to get on up there (don't remember the number right now, it should be stamped on the switch) to pull it in. You will have to evacuate the system prior to removing that switch. Is the site glass on the dryer clear? When it is you have the correct charge, assuming you are running r12 freon.

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Jim