Musty Odor from HVAC System (Reprogram HVAC Control Module to Enable Afterblow Function)

This bulletin is being revised to add the 2006 model year and update the calibration release date. Please discard Corporate Bulletin Number 05-01-39-002 (Section 01 -- HVAC).

Some customers may comment on a musty odor from the Heating, Ventilation and Air Conditioning (HVAC) system. This condition occurs most often on initial start up after the vehicle was driven on a hot humid day.

This condition may be caused by condensate build-up on the evaporator core, which does not evaporate by itself in high humidity conditions.

Important: The afterblow function should not be enabled until after the purpose and operation of it is explained to your customer and they approve of the change. Once the afterblow function is enabled there are no calibrations currently released to disable it.

Technicians are to reprogram the HVAC Control Module with an updated software calibration that will enable the afterblow function. The new calibration will be released beginning with TIS satellite data update version 2.0, which was made available February 5, 2006. The blower motor will turn on approximately 10 minutes after the vehicle is shut off. The blower motor will run continuously for 10 minutes at a 30% duty cycle. The afterblow function will only activate if the air conditioning compressor was engaged during conditions of high ambient temperature. If the vehicle is started within 10 minutes of the last key off, the afterblow function from the previous key cycle will be cancelled.

Technicians should not attempt to reprogram a vehicle with a Manual Temperature Control HVAC system (RPO CJ3).

Technicians should perform this HVAC Control Module reprogram instead of installing the Electronic Evaporator Dryer Module Kit referred to in the Air Conditioning Odor bulletin, Corporate Bulletin Number 99-01-39-004A .

For vehicles repaired under warranty, use: