GM Service Manual Online
For 1990-2009 cars only

Caution: This procedure should only be performed on a cold car. irritating vapors may be formed if the disinfectant contacts hot engine components. Disinfectant can cause substantial but temporary eye injury. Do not get in eyes or clothing. Wash thoroughly with soap and water after handling.

Some vehicles may exhibit undesirable odors emitted from the air conditioning system primarily at startup in hot, humid climates. The odor may diminish as the system continues to operate. This odor may result from one or both of the following conditions:

    • Foreign material in the heater/evaporator case
    • Microbial growth on the evaporator core

In order to address this condition, perform the following procedure:

    • Clean and disinfect the evaporator core.
    • Enable the afterblow mode.

Enabling Afterblow Mode

Enable the afterblow mode in order to prevent the reoccurrence of odor complaints. This function is used in order to remove the condensation from the evaporator core following a drive in high temperature conditions. Enabling of the afterblow mode allows the blower motor to turn ON 45 minutes after the vehicle ignition is turned OFF if the following conditions are true:

    • If the compressor was engaged for more than 3 minutes total run time during the last ignition cycle
    • If the outside temperature at ignition OFF was above 27°C (80°F)

The blower will then run for 3 minutes and turn OFF.

Enable the afterblow mode with a scan tool .

Important: The customer should be advised when this mode is enabled. The mode function and purpose should be explained to the customer.