For 1990-2009 cars

The Heating, Ventilation and Air Conditioning (HVAC) system is divided into three sections. The first, Heating, Ventilation and Air Conditioning, has all procedures that pertain to a HVAC component or function that are not specifically associated with an automatic or manual control system. The second, HVAC Systems-Manual, has all procedures specific to the manual control system. The third, HVAC Systems-Automatic, has all the procedures specific to the automatic control system.

For systems with DTCs, begin the system diagnosis with the following procedures:

• | Diagnostic System Check - HVAC Systems - Manual in HVAC Systems-Manual

• | Diagnostic System Check - HVAC Systems - Automatic in HVAC Systems-Automatic

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 Class 2 serial data circuit.

The use of the Diagnostic System Check will identify and lead the technician to the correct diagnostic procedure.

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 normal operation. The HVAC Description and Operation information is divided into:

• | Air Delivery Description and Operation in HVAC Systems-Manual

• | Air Temperature Description and Operation in HVAC Systems-Manual

• | Air Delivery Description and Operation in HVAC Systems-Automatic

• | Air Temperature Description and Operation in HVAC Systems-Automatic

The Air Delivery Description and Operation contains the following topics:

• | HVAC Control Components

• | Air Speed

• | Air Distribution

• | Recirculation Operation

• | Automatic Operation

The Air Temperature Description and Operation contains the following topics:

• | HVAC Control Components

• | Heating and A/C Operation

• | Automatic Operation

• | Engine Coolant

• | A/C Cycle