For 1990-2009 cars

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

• | Control Assembly Description

• | HVAC Compressor/Condenser Fan Circuit Description

• | HVAC Blower Controls Circuit Description

• | Relays and Sensors Description

• | Air Conditioning (A/C) Compressor Control Module Description

### Visual/Physical Inspection

• | Inspect for aftermarket devices which could affect the operation of the HVAC System. Refer to Checking Aftermarket Accessories in Wiring Systems.

• | Inspect the easily accessible or visible system components for obvious damage or conditions which could cause the symptom.

• | Inspect all related ground points for being clean and tight.

### Intermittent

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

### Symptom List

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

• | HVAC Compressor Clutch Does Not Engage

• | HVAC Compressor Clutch Does Not Disengage

• | Blower Motor Inoperative at Any Speed

• | Blower Motor Low Speed Inoperative

• | Blower Motor Inoperative Med-1

• | Blower Motor Inoperative Med-2

• | Blower Motor Operates at High Speed Only

• | Blower Motor High Speed Inoperative

• | Blower Motor Always On

• | Condenser Fan Inoperative

• | Condenser Fan Always On

• | System Performance Test

• | Leak Testing

• | TXV A/C System Diagnosis (Insufficient Cooling)

• | Heating Insufficient

• | Heat Excessive (Heater Mode)

• | Heat Excessive (Vent Mode)

• | Air Delivery Improper

• | Noise Diagnosis - A/C System

• | Odor Diagnosis

• | High or Low Temperature Control Effort