HVAC - Automatic - Diagnostics

Inspection of HVAC Control Module And Its Circuit

HVAC control module and its circuits can be checked at HVAC control module wiring couplers by measuring voltage.

CAUTION: HVAC control module can not be checked by itself. It is strictly prohibited to connect voltmeter to HVAC control module with couplers disconnected from it.

Voltage Check

G77-1-G77-5:

G77-6-G77-30:

1. Remove HVAC control module referring to HVAC Control Module Removal and Installation.
2. Check voltage at each terminal.

NOTE: As each terminal voltage is affected by the battery voltage, confirm that it is 11 V or more when ignition switch is ON.

Reference Waveform






NOTE: The shape of waveform varies with engine coolant temperature.

Reference Waveform:

Waveform at 0 °C (32 °F)

Reference Waveform:

Waveform at 40 °C (104 °F)

Reference Waveform:

Waveform at 80 °C (176 °F)