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What controls compressor cycling in TXV system W/O evap temp sensor?

webbch on Mon June 23, 2014 4:13 AM User is offlineView users profile

My dad has a '69 camaro, with a retrofitted A/C (installation manual with system description here ). Although he has expressed that it isn't cooling well, I haven't done any diagnosis yet - just trying to fully understand how the system operates.

The system is a TXV setup. I'm used to an evap temp sensor controlling the compressor cycling. In the camaro's setup, the TXV has a sensing bulb that controls refrigerant flow, and what appears to be a high pressure switch on the receiver/drier. Could someone explain how that controls the cycling of the compressor? My only explanation is that when the sensing bulb on the TXV gets cold enough, it fully shuts off refrigerant flow, which causes you to build high pressure in the condensor, thus shutting off the compressor via the pressure switch in the receiver drier. Is that correct? I think I'm missing something...


Edited: Mon June 23, 2014 at 4:19 AM by webbch

Dougflas on Mon June 23, 2014 7:02 AM User is offline

The system has a thermostat that senses evap temp. That in turn will cycle the compressor. The original system did not cycle the compressor and the compressor ran continuously. The POA controlled evap pressure so the system did not freeze up. The txv bulb senses the temp of the suction line and makes sure the evap is filled with refrigerant.

webbch on Tue June 24, 2014 12:41 AM User is offlineView users profile

Thank you. After reading your post and looking over the installation details again, I did see the thermostatic switch on the evap for controlling compressor cycling. That makes much more sense to me now.

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