Circuit/System Description
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The HVAC control module monitors the low side refrigerant pressure through the A/C refrigerant pressure sensor. The HVAC control module supplies a 5-volt reference and a low reference to the sensor. Changes in the A/C refrigerant pressure cause the sensor signal to the HVAC control module to vary. When the pressure is high, the signal voltage is high. When the pressure is low, the signal voltage is low. When pressure is high, the HVAC control module sends a message to the ECM to turn on the cooling fans on. When pressure is too high or too low, the HVAC control module will not allow the A/C compressor to operate.