Air Conditioning (A/C) Compressor

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Fig 1: Identifying A/C Pressure Sensor

Courtesy of VOLVO CARS OF NORTH AMERICA.

The air conditioning (A/C) pressure sensor detects the pressure in the high-pressure side of the air conditioning (A/C) system. This is so the engine control module (ECM) can control:

start-up of the engine cooling fan (FC) step 2
start-up of the engine cooling fan (FC) step 3
stopping the compressor if the pressure in the air conditioning (A/C) is too high
constant idle speed compensation for the air conditioning (A/C) compressor load.

The sensor is linear. It is grounded in the control module and supplied with a 5 Volt current from the control module. A linear signal (between 0-5 V depending on the pressure in the air conditioning (A/C)) is transmitted to the control module. Low pressure produces low voltage, high pressure produces high voltage.

The engine control module (ECM) can diagnose the air conditioning (A/C) pressure sensor. The sensor value can be read off using appropriate diagnostics tool.

The air conditioning (A/C) pressure sensor is positioned on the high pressure delivery line for the air conditioning (A/C) system.