GM Service Manual Online
For 1990-2009 cars only

Odor Correction SRE: USE SIO #787457

Eliminating Air Conditioning Odor

Odors may be emitted from the air conditioning system primarily at start up in hot, humid climates. The following conditions may cause the odor:

    • Debris is present in the HVAC module.
    • Microbial growth on the evaporator core

When the blower motor fan is turned on, the microbial growth may release an unpleasant musty odor into the passenger compartment. To remove odors of this type, the microbial growth must be eliminated. Perform the following procedure:

Deodorize the evaporator core using Deodorizing Aerosol Kit.

Perform the following steps in order to deodorize the A/C system:

  1. Ensure that the plenum which draws outside air into the HVAC module is clear of debris.
  2. Disable the A/C compressor clutch operation by disconnecting the clutch coil electrical connector.
  3. Dry the evaporator core by performing the following steps:
  4. 3.1. Start the engine.
    3.2. Select the warmest temperature setting.
    3.3. Select the recirculation mode.
    3.4. Run the blower motor on high for 10 minutes.
  5. Locate an area in the air conditioning duct between the blower motor and the evaporator core downstream of the blower motor.
  6. Drill a 3.175 mm (0.125 in) hole where the hole will not interfere with or damage the following components:
  7. • The blower motor
    • The evaporator core
    • Any other operating part the of system
  8. Wear safety goggles and latex gloves in order to perform the following actions:
  9. 6.1. Select the maximum blower speed.
    6.2.  Insert the deodorizer extension tube into the hole to the mark on the extension tube.
    6.3. Use short spray bursts and vary the direction of spray for a 2-3 minute period of time.
  10. Shut the engine OFF. Allow the vehicle to sit for 3-5 minutes.
  11. Seal the 3.175 mm (0.125 in) hole with body sealer or RTV gasket compound.
  12. Start the engine.
  13. Operate the blower motor on high for 15-20 minutes to dry.
  14. Reconnect the A/C compressor clutch coil electrical connector.
  15. Verify proper clutch operation.