For 1990-2009 cars

# INFO. ON WHITE DUST BLOWING FROM HVAC VENTS

#### SUBJECT: INFORMATION ON WHITE DUST BLOWING FROM HVAC VENTS

#### VEHICLES AFFECTED: 1993 " B, C, D, E, F, H, K, W" MODELS

THIS IS A DCS MESSAGE.

Some owners of 1993 B, C, D, E, F, H, K and W cars may comment on white dust or flakes blowing from the HVAC vents. Vehicles built during February, March, and April, 1993 may exhibit this condition. This dusting or flaking is caused by excess silicate coating flaking from the evaporator core. The flaking material is a non-crystalline silicone dioxide which represents no health or toxicity risk. This flaking condition is initiated by usage of the A/C system including wetting and drying cycles of the evaporator core. The duration and amount of dust is variable and will disappear with time and usage. With regular A/C usage, some vehicles have stopped flaking within 2 or 3 days, although other vehicles may persist for several weeks.

Even though this condition will disappear with usage, some customers may request immediate correction. Service requires replacing the evaporator core. Although the evaporator core can be replaced per service manual procedures, the customer should be advised this is a complex operation including discharging and recharging the A/C refrigerant system. Since the condition will disappear, the options should be reviewed with the customer. If, in order to satisfy the customer, the evaporator core needs to be replaced, please perform the procedure immediately.

In addition to normal service procedure, the evaporator case and duct system should be thoroughly cleaned. With evaporator out of vehicle, blow compressed air through evaporator case to loosen any remaining dust that may be on the walls of the duct work and move it up toward outlet vents. Vacuum inside of evaporator case and any accessible ducts, then wipe with a damp cloth before installing evaporator.

After replacement of the evaporator core, the HVAC system should be cycled through all modes on high blower speed to dislodge any remaining particles. Thoroughly vacuum any surface of the vehicle where dust may have accumulated. Cleaning of the ducts and case is particularly critical in avoiding customer comebacks from loose material blowing from the HVAC outlet.

When cores are available from GMSPO they will not be coated with silicate.

This bulletin will be updated shortly when more information becomes available.

General Motors bulletins are intended for use by professional technicians, not a "do-it-yourselfer". They are written to inform those technicians of conditions that may occur on some vehicles, or to provide information that could assist in the proper service of a vehicle. Properly trained technicians have the equipment, tools, safety instructions and know-how to do a job properly and safely. If a condition is described, do not assume that the bulletin applies to your vehicle, or that your vehicle will have that condition. See a General Motors dealer servicing your brand of General Motors vehicle for information on whether your vehicle may benefit from the information.