For 1990-2009 cars

Symptom | Cause | Correction
--- | --- | ---
Under certain high humidity climate operating conditions, a musty odor may develop. The odor develops due to a microbial growth in the evaporator area. This odor is generally temporary. As the climate conditions change, the condition will disappear. If the mold/mildew odor persists refer to Odor Correction for the odor elimination procedure.
A musty smell. | Mold/mildew growth exists in the evaporator fins. | Clean the evaporator fins. Refer Odor Correction and/or Air Conditioning Evaporator Core Replacement .
A clog exists in the evaporator drain. | Clean the evaporator drain.
Interior water leaks exist in the body. | Seal the body.
A coolant smell. | A coolant leak exists. | Inspect the heater hoses and the core for leakage. Refer to Heater Hoses Replacement and/or Heater Core Replacement .
A refrigerant oil smell. | A refrigerant leak exists at the evaporator. | Inspect the evaporator and the fittings for refrigerant leakage. Refer to Leak Testing .