For 1990-2009 cars

The Heating, Ventilation and Air Conditioning (HVAC) system is divided into 3 separate sections. The first, Heating, Ventilation and Air Conditioning, has all procedures that pertain to a HVAC component or function that is not specifically associated with the manual or automatic control system. The second, HVAC Systems - Manual, has procedures specific to the Manual control system and the third, HVAC systems - Automatic, has procedures specific to the automatic control system. The DTCs and scan tool data that support the manual HVAC system are also relevant for the automatic HVAC system. To minimise data duplication this information is located in HVAC Systems - Automatic.

Begin the system diagnosis with the Diagnostic System Check - Vehicle . The diagnostic system check will provide the following information:

• | The identification of the control modules which command the system.

• | The ability of the control modules to communicate through the serial data circuit.

• | The identification of any stored diagnostic trouble codes (DTCs) and their status.

The use of the diagnostic system check will identify the correct procedure for diagnosing the system and where the procedure is located.

Review the description and operation information to help you determine the correct symptom diagnostic procedure when a malfunction exists. Reviewing the description and operation information will also help you determine if the condition described by the customer is an abnormal operation. The HVAC description and operation information is divided into the following:

• | Air Delivery Description and Operation -- Manual or Air Delivery Description and Operation -- Automatic.

• | Air Temperature Description and Operation -- Manual or Air Temperature Description and Operation -- Automatic.

The air delivery description and operation contains the following topics:

• | HVAC control components.

• | Air speed.

• | Air distribution.

• | Recirculation operation.

The air temperature description and operation contains the following topics:

• | HVAC control components.

• | Heating and A/C operation.

• | Engine coolant.

• | A/C cycle.