GM Service Manual Online
For 1990-2009 cars only

Under certain climate and operating conditions, a musty odor may develop. Growth in the evaporator core causes the musty odor. This odor is generally temporary. As climate conditions change, the odor disappears. If the odor persists, clean the evaporator core with the appropriate cleaner.

Important: Do not operate the A/C compressor at any time during this procedure.

  1. Clear all debris from the plenum duct that draws in air from the outside.
  2. Use the following procedure in order to dry the evaporator core:
  3. 2.1. Start the engine.
    2.2. Turn the blower on HIGH, with the temperature set on maximum for 10 minutes.
    2.3. Turn the engine OFF.
  4. Shake the deodorizer spray can well. Insert the extension tube into the nozzle on the can.
  5. Remove the blower motor resistor. Refer to Blower Motor Resistor Replacement .
  6. Start the engine. Turn the blower on HIGH.
  7. Using safety goggles and latex gloves, insert the extension tube into the resistor hole past the mark on the tube. Spray with short bursts for 2-3 minutes.
  8. Turn the engine OFF. Let the engine sit for 3-5 minutes.
  9. Start the engine and run the blower on HIGH for 15-20 minutes in order to dry the evaporator.