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A/C - Musty/Mildew Odors From Vents



TSB: 07-001/07


NOTE: This bulletin replaces 07-001/03. Please update your records accordingly.

BULLETIN NOTE: This bulletin supersedes 07-001/03 issued 05/02/2003. The APPLICABLE MODEL(S)/VINS and REPAIR PROCEDURE have been revised.

APPLICABLE MODEL(S)/VINS^ 2003-2007 Mazda6
^ 2004-2007 Mazda3
^ 1998-2002 626
^ 1998-2003 Protege
^ 2002-2003 Protege5
^ 2000-2003 MPV
^ 1998 MPV
^ 1998-2002 Millenia
^ 1999-2003 Miata


A musty/mildew type odor may come from the vents when the air conditioning (A/C) system is operating. It is most noticeable when the A/C is first turned ON. This odor is the result of mold growth in the A/C evaporator/cooling unit which is caused by condensation, dust, and pollen within the cooling unit. This condition is usually worse during high humidity conditions. Mazda Air Cooling Coil Coating is available to encapsulate the mold to reduce odors. If the product is properly applied, it can effectively reduce the musty/mildew odor for up to three years.

NOTE: See parts information for Mazda Air Cooling Coil Coating and Kit part numbers.

This treatment provides a durable coating that will aid to prevent biological reactions that lead to odor concerns. It is applied to the evaporator in a misted form that is introduced by way of the cabin air filter, the re-circulate door, the blower motor resistor access, or the blower motor air intake. Proper application requires the evaporator surface to be:

^ Relatively clean and free of leaves, dust build-up and debris.

^ Thoroughly dried, and the product cured onto it after application.

^ A/C odor is not unique to Mazda vehicles as it will occur in other makes and models.

^ To minimize A/C odor, suggest the following to the customers:

^ Keep the cooling unit dry by leaving the blower fan ON (at least on low), even if the A/C is not being used.

^ In low humidity (dry) conditions, keep the ventilation system in the FRESH mode all the time, or as much as possible.

^ In high humidity conditions, or if the air has a lot of dust or pollen, keep the system in the RECIRCULATION mode.

^ A few minutes before reaching a destination, turn the A/C OFF, but leave the blower fan ON. This stops the accumulation of condensation on the evaporator/cooling unit, and it helps dry the inside of the cooling unit.

Customers having this concern should have their vehicle repaired using the following procedure.


1. Verify customer concern.

2. Verify the evaporator drain has no blockage.

3. Apply Mazda Air Cooling Coil Coating according to the instructions. Refer to the table above for the applicable repair instructions.

NOTE: ^ Follow the instructions completely to ensure an effective repair. If insufficient care is taken on the drying sequence of product, the coating will not last, and the concern will reoccur.

^ If the odor is still present after treatment, it may be necessary to remove and clean the evaporator, the evaporator foam, and the inside of the cooling unit housing with a mild dish soap and water solution. To avoid damage to components, do not clean with bleach. See Workshop Manual section 07 for removal instructions.

^ When using this product, avoid skin and eye contact. Wear safety glasses and gloves, and avoid breathing vapors.

^ Read all the safety and first aid instructions on the back of the Mazda bottle.

4. Verify repair.