Control Module HVAC: Description and Operation

A/C AMPLIFIER

A/C amplifier is installed to the lower evaporator case.
It controls operation of the compressor magnet clutch and condenser fan motor according to the signals from the sensors and ECM which detect the state of the engine and driving conditions.

Main system control functions are as follows (at A/C switch ON).

- Magnet clutch delay control: 0.12 second
(Time since A/C signal is sent from A/C amplifier to ECM till A/C ON signal is sent back from ECM to A/C amplifier.)

- A/C ON-OFF control:

High refrigerant pressure:
above 3140 kPa (32 kg/sq.cm, 455 psi) OFF
below 2550 kPa (26 kg/sq.cm, 370 psi) ON

Low refrigerant pressure:
below 196 kPa (2.0 kg/sq.cm, 28.4 psi) OFF
above 226 kPa (2.3 kg/sq.cm, 32.7 psi) ON

- Evaporative temperature:

A/C switch ON
below 2.5 °C (36.5 °F) OFF
above 4.0 °C (39.2 °F) ON

ECO switch ON
below 8.0 °C (46.4 °F) OFF
above 9.5 °C(49.1 °F) ON

ECM
The A/C amplifier outputs A/C signal to ECM when A/C ON conditions are satisfied on the A/C amplifier side. (The air conditioning system does not turn ON in this state.) When ECM detects through the A/C signal that A/C ON conditions are satisfied on the A/C amplifier side, it uses the A/C signal as one of the factors to output A/C ON signal and to control idle air control valve and fuel injection respectively.

- Engine coolant temperature:
above 110 °C(230 °F) OFF
below 103 °C(217 °F) ON

- While engine cranking with
starter on OFF

- Engine speed:
below 6600 r/min OFF
above 6200 r/min ON
below 700r/min ON
above 500 r/min OFF

- While accelerating rapidly:
(when throttle opened 80% within 3.5 seconds) OFF