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On TXV systems does compressor cycle ? Intended function of high pressure switch
Posted: Tue Aug 13, 2019 5:27 pm
by r-mm
I have a 1989 BMW 325i with an expansion valve as attached. On such a system does one expect the compressor to cycle on and off via the high pressure switch on the receiver/dryer, or does the expansion valve control the flow of refrigerant and therefore how hard the compressor is working?
Re: On TXV systems does compressor cycle ? Intended function of high pressure switch
Posted: Tue Aug 13, 2019 5:59 pm
by Cusser
On my 1988 Mazda truck, and my 1998 and 2004 Nissan Frontiers - all which have expansion valve systems - the de-icer switch on the evaporator case (which has a sensor in the evaporator fins) makes their compressors cycle.
Re: On TXV systems does compressor cycle ? Intended function of high pressure switch
Posted: Wed Sep 04, 2019 2:38 pm
by JeremyB
The TX valve just controls superheat of the evaporator. Depending on conditions, the evaporator could be at 35 degrees or 55 degrees with the same amount of superheat. Once the evaporator pressure (and temperature) drops below the switch setpoint, it opens to prevent evaporator freezup.
Not familiar with that BMW, but a high pressure switch on the receiver will shut off the compressor if the high side exceeds maximum pressure of the switch.