HVAC Control Components
HVAC Control Assembly
The HVAC control assembly interfaces between the operator and the HVAC system to maintain air temperature and distribution settings. The air temperature and mode doors are controlled by cables. The recirculation actuator is electrically controlled.
The HVAC control module supports the following features:
| Feature | Availability |
|---|---|
| Afterblow | NO |
| Purge | NO |
| Personalization | NO |
| Actuator Calibration | NO |
Evaporator Temperature Sensor
The evaporator temperature sensor is a two-wire negative temperature co-efficient thermistor. The sensor operates within a temperature range of -40 to +85°C (-40 to +185°F). The sensor is installed at the evaporator and measures its temperature. If the temperature drops under 1°C (34°F), the compressor will be switched off in order to prevent a frozen evaporator.
A/C Refrigerant Pressure Sensor
The engine control module (ECM) monitors the high side refrigerant pressure through the signal circuit of the A/C refrigerant pressure sensor. The ECM supplies a 5V reference and a low reference to the sensor. Changes in the A/C refrigerant pressure cause the sensor signal to the ECM 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 ECM commands the cooling fans on. When pressure is too high or too low, the ECM will inhibit activation of the A/C compressor.
A/C Compressor
The A/C compressor is belt driven and operates when the magnetic clutch is engaged. When the A/C switch is pressed, an A/C request message to the ECM. If the ECM determines that conditions are acceptable for A/C operation, it will ground the A/C compressor clutch relay control circuit, energizing the A/C compressor clutch relay. With the relay contacts closed, battery voltage is applied to the A/C compressor clutch. The A/C compressor clutch will engage and the compressor will operate.