2008 Fan Afterblow Function Description?

jscan · November 23, 2010

can anyone describe in detail "how and when" the fan afterblow function operates? dealer said they turned on the setting to my 08 sierra 2500 for the musty odor that emits from my vents. have not heard it come on yet. i live in CT and it was about 58 degrees today. i do understand that it turnes on after truck is off...i waited and heard nothing from the fan. even removed blower foam/plastic cover to hear and heard nothing.

mnm8977 · November 28, 2010

The dealer did the same thing in my 08 Silverado. As for what conditions need to be present for it to work, I have no clue, but I have found it on a couple of times. It is almost unnoticable because it blows at a very low speed. Since they turned it on I have had no problems though. Basicaly the way it works is after the vehicle is shut off the BCM turns the blower motor on a few min after shut down. This circulates air and helps dry the evaporator core from the condensation caused by high humidity. The smell is caused from mold and mildew that love damp places. The afterblow function solves this problem. If you still have the problem afterwords, spray a product called frgifresh in the HVAC intake in the cowling.

jscan · December 2, 2010

thanks, that was much more info. that i have received than from the actual dealer.

minibike132 · November 28, 2010

When afterblow has been enabled by the scan tool the blower motor will operate at 68 percent blower speed for 2 minutes 30 seconds to 4 minutes after the engine has been in Key OFF for 30 minutes.

The following conditions must be met for the HVAC module to operate the afterblow:

• The outside air temperature must be at least 21°C (70°F).

• The A/C compressor must have operated during the latest key cycle.

• The engine must be turned off for at least 30 minutes.

• The system voltage must be at least 12 volts.