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 module can communicate via the serial data link.

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

•	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.
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: