GM Service Manual Online
For 1990-2009 cars only

Important: Review the system operation in order to familiarize yourself with the system functions. Refer to HVAC Blower Controls Circuit 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.
    • If equipped, inspect the passenger compartment air filter for complaints of insufficient air flow.

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:

    •  Blower Motor Inoperative at Any Speed
    •  Blower Motor Low and Medium Speeds Inoperative
    •  Blower Motor Operates at High Speed Only
    •  Blower Motor High Speed Inoperative
    •  Blower Motor Always On
    •  Vacuum System
    •  Heater Air Inoperative
    •  Defrost Air Inoperative
    •  Instrument Panel Outlets Inoperative
    •  Air Recirculation Inoperative
    •  Air Recirculation Always On
    •  Temperature Control Inoperative
    •  Cooling Insufficient - Air Conditioning (A/C) System
    •  Defrosting Insufficient
    •  Heating Insufficient
    •  Noise Diagnosis
    •  Cold Drafts on Floor
    •  Odor Diagnosis