Testing the Afterblow feature on a 2012 Silverado...
 

So I had to take my truck back in for a second time so far for a musty, mildew smell that happens when I first turn on the A/C in the morning. First time they deodorized the evaporator coil. This time they did the same thing, plus turned on the "Afterblow" feature for the A/C. I haven't noticed it kicking on yet though. How long does it take to turn on after shutting the truck off? Some site say 10 minutes, other say 30. I just want to test the feature out and make sure it is working.

Make sure the evap drain isn't plugged or the hose kinked.

When mine does that I run the heat for a few minutes to help dry things a bit before shutting down.

El Baz , does yours have the afterblow feature turned on? Basically the fan kicks on after the truck shuts off , and drys out the system of evaporation. I'm curious to the time it takes for it to kick on after the vehicle is shut off, some say 10 minutes, others say 30....

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.

Mine's an '07 LTZ. I just bought it and haven't got all the way through the very exciting owners manual yet but so far no mention of this feature. From Tech2's post it sounds like something you need a scantool (dealership) to turn on(?).

I live in Colorado so we don't have a big problem with moisture and/or condensation too often. I noticed it was a bit funky one afternoon so I just ran the heater while the turbo cooled down. No more funkiness.

what I'm looking for is a fail proof method to make it activate so I know it's working. Any ideas?

you can always try turning the AC off but leave the fan on,a few miles before you reach your destination...
I do not have the after-blow feature enabled and from time to time I get the musty smell so I just turn the AC off and turn the fan on high a mile or 2 before I get home... there is usually enough cold left in the system to make the 102 temp outside manageable for the short period and it seems to do the job :)