1985-1998 [Subscribe to Daily Digest] |
You have a couple of issues and the pressure switch is not one of them.
Were these pressures at engine idle or with the engine running at 1500-2000? Was the 250psi on the high side with the main radiator fan running? What was the outside air temperature when the pressures were read? How well is the system cooling?
I think your mechanic is more familar with accumulator systems as used in American cars rather than receiver/drier systems in most imports. The accumulator systems use a pressure switch in the low side of the system to control compressor operation and prevent the evaporator from freezing. In the receiver/drier system, the pressure switch is attached to the receiver/drier in the high side line. In your case, the pressure switch is seeing a steady 250 psi so your problem is not there. An anti-frost switch located in the evaporator is used the receiver/drier systems to shut down the compressor if the evaporator starts to freeze instead of a low pressure control switch as in the accumulator systems.
I would explore the anti-frost switch first by jumping the wires. The switch in your car may be adjustable. Look for a mini-screw under the wires. I think you will find this is where your problem lies.
Depending on outside air temp, fan operation and engine speed when the pressures were taken, I also think you might have a low charge. My recollection is that low pressure on the 9000 in normal operation bottoms out around 25psi on a warm day. My best guess is either low charge and/or a problem with your expansion valve that's causing the low side to get too low.
The expansion valve modulates refrigerant flow by opening and closing to keep a steady atomization of refrigerant as it flows into the evaporator. If it's stuck closed or near closed, it will create a blockage which creates artifically high pressure on the high side and artificially low pressure on the low side at less than full refrigerant charge. I am not sure which valve was used on your car since the 1992 was a sort of transition year with the a/c.
posted by 64.222.108...
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