Does anyone have a spec for the operating pressure for a '91 A/C system? I'm not sure if I'm low on refrigerant or there is some type of switch problem, either pressure or engagement. The system is now 134 with a March pulley setup and Sanderson compressor. When the clutch engages it blows ice cold air however when I select AC on the control panel it does not turn on every time. This seams to occur mostly when the engine is warm and generally the system engages when the engine is cold or first started. The condenser is a year old.

Thanks
Roy

 

 

Ensure that your compressor is getting the proper signal from the various controls. I don't recall what type A/C system these are (TXV/Orifice tube) but the compressor will not engage if certain conditions are met. There is a thermal limiting switch on the compressor that will disable the compressor if it is too hot. An in-range failure of this switch may cause the problem you are having. Another issue you could have is water vapor in the A/C if the system was open to the atmosphere for a period of time. The only way to fix this is bringing the system into deep vacuum.

As a general rule, the operating pressure of the high side will be from two to three times the ambient temperature, where the low side will be between 30 and 50 PSI depending on the high side pressure and ambient temperature.

 

Thanks, ok brain fart, Sanden compressor! system holds 36oz
Roy

 

Cool, I started with a 1984 Belinetta. Thanks for the input, does anyone know where the orifice tube is located?

Thanks again,
Roy