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Tahoe / Yukon Service Manual

Symptoms - Heating, Ventilation, and Air Conditioning

  1. Perform the Diagnostic Starting Point - 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.  Automatic HVAC Description and Operation  or  Heating and Air Conditioning System Description and Operation Visual/Physical Inspection Inspect for aftermarket devices which could affect the operation of the HVAC System. Checking Aftermarket Accessories Inspect the easily accessible or visible system components for obvious damage or conditions which could cause the symptom. Verify the A/C compressor clutch turns freely and is not seized. The A/C compressor will not operate in cold outside air temperatures. The following could 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 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 Intermittent Faulty electrical connections or wiring may be the cause of intermittent conditions. Testing for Intermittent Conditions and Poor Connections Symptom List Refer to a symptom diagnostic procedure from the following list in order to diagnose the symptom: Leak Testing Noise Diagnosis - HVAC Module Noise Diagnosis - Air Conditioning (A/C) System Noise Diagnosis - Blower Motor Odor Diagnosis