Important: The following steps must be completed before using the symptom tables.

1. Perform the Diagnostic System Check - Vehicle , before using the Symptom Tables in order to verify that all of the following are true:

•	There are no DTCs set.

•	The control modules can communicate via the serial data link.

2. Review the system operation in order to familiarize yourself with the system functions. Refer to the following information:

•	Air Delivery Description and Operation

•	Air Temperature Description and Operation

1. Inspect for aftermarket devices which could affect the operation of the HVAC System. Refer to Checking Aftermarket Accessories .
2. Inspect the easily accessible or visible system components for obvious damage or conditions which could cause the symptom.
3. Verify the A/C compressor clutch turns freely and is not seized.
4. Verify that the customer is using the correct key to enable personalization and is not inadvertently activating auxiliary HVAC controls.
5. The A/C compressor will not operate in cold outside air temperatures. Refer to Air Temperature Description and Operation .
6. The following conditions may cause window fogging:

•	Wet carpet or mats

•	High humidity

•	Interior water leak

•	Blocked A/C evaporator drain tube

•	Maximum passenger capacity

•	Blocked body pressure relief valves

7. Inspect the air distribution system for causes of reduced air flow:

•	Obstructed or dirty passenger compartment air filter, if equipped

•	Blocked or damaged air inlet or outlet vents

Faulty electrical connections or wiring may be the cause of intermittent conditions. Refer to Testing for Intermittent Conditions and Poor Connections .

Refer to a symptom diagnostic procedure from the following list in order to diagnose the symptom: