HVAC runs when truck is shut down?

[towerrigger]

I have a 2015 Sierra AT, 6.2L full load. almost touching 100,000km on the clock. I have been having this random issue or at least I think it is random. I will get to my destination and shut the truck off and get out, lock it with key fob. I could come back 10-15min later and hear the HVAC fan running. no lights on the dash and none of the controls other than the defrost button will shut it off or putting in the key and turning it to run. Sometimes it will run for 2 min other times it's short and runs 30 seconds. I have brought it to the dealer several times and they are not interested in looking into it. Has anyone else run across this? Is it possible that this is supposed to happen to clear out the condensation in the system from running the AC?

[2017SierraSLT]

A customers Mazda SUV did this. It was a simple fix. The blower motor relay was defective, allowing the motor to run after the key was turned off. Try switching the relay.

[newdude]

Sounds like the afterblow feature is turned on. It allows the blower motor to run and dry off the AC evaporator in the blower box to prevent odors.

[Spurshot]

... Is it possible that this is supposed to happen to clear out the condensation in the system from running the AC?

 

I was thinking there were some threads about evaporator condensation causing mold/stink, where there was some discussion about a post shutdown blower run to help with the issue. Maybe some of the techs or someone with info on this will come along.

[towerrigger]

 

I was thinking there were some threads about evaporator condensation causing mold/stink, where there was some discussion about a post shutdown blower run to help with the issue. Maybe some of the techs or someone with info on this will come along.

I did have the truck in for the smelly AC when it was new. I can't find in any of my records that they did a software upgrade back then. The dealer was supposed to check and see if there was a new update available but the tech forgot about it.

[newdude]

I did have the truck in for the smelly AC when it was new. I can't find in any of my records that they did a software upgrade back then. The dealer was supposed to check and see if there was a new update available but the tech forgot about it.

 

 

I'm betting they turned on the afterblow feature as I mentioned above.