Pressure sensors are used to monitor pressure in the AC system in a similar way that pressure switches function. The main difference is that these devices must be diagnosed with either a voltmeter or a scan tool. These sensors operate by varying the signal voltage as the AC pressure rises and falls. This signal voltage can be seen on a scan tool or by back-probing the signal wire with a voltmeter. Replacing these devices involves the same techniques and cautions as replacing pressure switches.
The AC pressure sensor connects to the AC system the same way as the pressure switches that have the Schrader depressor. These sensors can be replaced without recovering the
