Diagnostic Starting Point-Heating, Ventilation and Air Conditioning

WARNING: This page is about a different car, the 2003 GMC Sierra, 2003 GMC Cab & Chassis Sierra, 2003 Chevrolet Silverado, and 2003 Chevrolet Cab & Chassis Silverado. However, it is still accessible from the selected car via links, so may be relevant.

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:

For Manual HVAC, refer to DIAGNOSTIC SYSTEM CHECK-HVAC-SYSTEM
For Automatic HVAC, refer to DIAGNOSTIC SYSTEM CHECK-HVAC SYSTEM

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:

For Manual HVAC, refer to AIR DELIVERY DESCRIPTION AND OPERATION
For Manual HVAC, refer to AIR TEMPERATURE DESCRIPTION AND OPERATION
For Automatic HVAC, refer to AIR DELIVERY DESCRIPTION AND OPERATION
For Automatic HVAC, refer to AIR TEMPERATURE DESCRIPTION AND OPERATION

The Air Delivery Description and Operation contains the following topics:

Air Speed
Air Distribution

The Air Temperature Description and Operation contains the following topics:

Heater Mode
A/C Mode
A/C Cycle