Air conditioning (A/C) pressure sensor

WARNING: This page does not describe the selected car, but rather 7 other vehicles, including the 2007 Volvo V70, 2006 Volvo V70, 2005 Volvo V70, 2004 Volvo V70, and 2003 Volvo V70. However, it is still accessible from the selected car via links, so may be relevant.

Fig 1: Air Conditioning Compressor

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:

engine cooling fan (FC) start
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. At 0.25 kPa or lower, the voltage is 0 V, at 3100 kPa the voltage is approximately 4.75 V. Low pressure results in low voltage, high pressure in high voltage.

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

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