Date: Thu, 17 Aug 2000 11:27:26 -0400 From: "David Dussault" <davidnopsamaultnet.mv.com> Subject: 94 Saab 900 - A/C Liquid Receiver Pressure switch
I have a 1994 Saab 900 with air-conditioning. I recently attempted to add some refrigerant to the system but found that the pressure switch loated on the liquid line receiver (between the condenser coil and expansion valve) is OPEN and holding out the A/C from operating. If I jump out the pressure switch the A/C seems to run and cycle normally. I am trying to determine if the switch is defective or if the switch has opened as a result of overcharging the system. I originally thought that this swtich was a LOW pressure cutout that halted A/C operation in the event that the refrigerant charge became too low but is it possible that this pressure switch is dual low pressure AND high pressure cutout or possibly even a float switch that monitors the level of liquid inside the receiver tank? Is anyone familiar with this safety cutout on the Saab A/C receiver and what conditions are supposed to cause the control to open(hi/lo pressure, float)? I could just arbitrarily bleed some of the R-12 refrigerant out to see if the control is open as a result of ovecharging but I hat to waste VERY expensive refrigerant in this excercise. The suction and head pressures at the compressor seem normal that is why I suspect a possible defective pressure control but I don't know what the cut-in and cutout pressures are. If I kew specifically what the cutout was supposed to do I could better troubleshoot the problem. Your feedback would be greatly appreciated.