GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 1997 🢒 Corvette 🢒 HVAC 🢒 HVAC Systems - Manual 🢒 Musty Smell

A/C Odor Diagnosis

Problem

Possible Cause

Correction

Musty Smell
    • Water leaks (body)
    • The evaporator drain is blocked.
    • There is mold or mildew on the evaporator core.
    • Locate and repair any water leaks. Refer to the appropriate repair procedure in Water Leaks.
    • Clean the evaporator drain.
    • Clean the evaporator. Refer to Eliminating Air Conditioning Oder.

Coolant Smell
    • The heater core is leaking.
    • The heater core pipes or hoses are leaking.
    • Replace the heater core. Refer to Heater Core .
    • Replace the heater core pipes or hoses. Refer to Heater Pipes or Heater Hoses .

Refrigerant Oil Smell

The evaporator core is leaking.

Replace the evaporator core. Refer to Evaporator Core .

Mold/mildew odor problem--Under certain climate and operating conditions a 'musty' odor can develop. The odor is caused by a microbial growth in the evaporator core. This odor is generally temporary, and as climate conditions change, the odor will disappear. Should the odor persist it may become necessary to clean the evaporator core with an appropriate cleaner.

Eliminating Air Conditioning Odor

Odors may be emitted from the air conditioning system primarily at start up in hot, humid climates. The odor may be the result of debris in the HVAC module or the growth of mold on the evaporator core. To address this condition, a service kit is available through GMSPO.

A single application of deodorizer GM P/N 12370470 will remove odor from the air conditioning system. Installation of a delayed blower control module is recommended to prevent the odor form returning. Should the delayed blower control module be used, refer to the installation instructions that come with the part.

Perform the following step to deodorize the air conditioning system:

  1. Make sure that the plenum that draws outside air into the HVAC module is clear of all debris.
  2. Disable the A/C compressor clutch operation by disconnecting the clutch coil electrical connector.
  3. Dry the evaporator core by:
    4. 3.1. Starting the vehicle.
    3.2. Setting the temperature control on maximum heat.
    3.3. Setting the system in a recirc mode.
    3.4. Running the blower motor on high for 10 minutes.
  4. Locate an area in the air conditioning duct between the blower motor and the evaporator core downstream of the blower motor.
  5. Drill a 1/8 inch hole where it will not interfere or damage the blower motor, evaporator core, or any other operating part of the system.
  6. Wearing safety goggles and latex gloves:
    7. 6.1. Keep the blower motor operating on high.
    6.2.  Insert the extension tube of the deodorizer GM P/N 12370470 into the hole, past the mark on the extension tube.
    6.3. Over a 2-3 minute period of time, dispense the contents of the can into the duct, using short spray bursts and varying the direction of the spray.
  7. Shut the engine OFF and let the vehicle sit for 3-5 minutes.
  8. Seal the 1/8 hole with body sealer or RTV gasket compound.
  9. Start the engine and operate the blower motor on high for 15-20 minutes to dry.
  10. Reconnect the A/C compressor clutch coil electrical connector and verify proper clutch operation.