Sierra 1500 2WD V8-5.3L Hybrid (2004)
Low Pressure Sensor / Switch: Description and Operation
A/C LOW PRESSURE SWITCH
The A/C low pressure switch protects the A/C system from a low pressure condition that could damage the A/C compressor or cause evaporator icing.
The HVAC control module applies 5 volts to the A/C low pressure switch signal circuit. The switch will open when the A/C low side pressure reaches
165-200 kPa (24-29 psi). This prevents the A/C compressor from operating. The switch will then close when A/C low pressure side reaches 275-310
kPa (40-45 psi). This enables the A/C compressor to turn back ON.
The low pressure switch uses refrigerant pressure to open and close a set of electrical contacts. When A/C request is authorized, the switch is closed and
shows normal status. During this state, the switch will show 0 volts on the A/C low pressure sensor signal circuit. When A/C request is denied due to a
low pressure condition, the switch will be open. During this state, the switch will show 5 volts on the A/C low pressure sensor signal circuit.
