A/C Pressure Sensor
An electronic A/C pressure sensor is mounted on the discharge line (high
side) of the A/C compressor suction/discharge hose assembly. The sensor output
to the PCM is variable. The sensor output to the PCM is dependent upon
pressure inside the line. The PCM communicates the status of the A/C system
pressure to the body control module (SBM) via class 2 serial data. A higher
pressure results in a higher voltage output. A/C pressure is constantly
monitored in order to perform the following functions:
| • | Disengage the A/C clutch if the pressures are higher than 2 968 kPa
(430 psi) |
| • | Disengage the A/C clutch if pressures are below 255 kPa
(37 psi) |
A/C Compressor Control Relay
The A/C compressor control relay cycles the compressor on and off by
energizing and de-energizing the compressor clutch coil.
With the ignition key on, a current of 12 volts is applied to
the relay common contact and one coil terminal. The PCM grounds the second
coil terminal under the following conditions:
| • | When the driver selects A/C mode |
| • | When the driver selects defrost mode |
| • | When all other requirements are met |
When the relay is energized, current passes through the relay contacts.
This action energizes the compressor clutch coil.
