I have a 2017suburban and I get a musty stink when I change from AC to Heat and back....Moreso when I set the temp to 22-4 degrees....and even more when it’s raining / humid so can’t even open windows lol.

cabin air filter is bull****. Doesn’t help.
I have done multiple Treatments dealer has done 2 and I have done a few Lysol treatments.
Any suggestions/ideas ?....anyone.....anyone ?

 

There is a dealer initiated via their diagnostic computer called a after blow option. It runs the blower for a few minutes after turning vehicle off to clear condensation from the evaporator to limit mold growth which is the source of the odor. Filter is before the evap. coil that's why it doesn't help.
Dealer is making money on treatments, make sure they turn that option on. It's a issue on many GM vehicles for a long time.

 

Hi! Thanks for the quick response.

I should have mentioned that I have the after-blow feature enabled already. My apologies.

I suspect the smell may be coming from the rear HVAC system - I don't believe after-blow is an option in the rear unit but I don't know, I have not confirmed this.

Either way, after-blow is not helping but thanks for positing

 

On our 2007 Tahoe I did clean the coil assembly and that really helped, but I found the best way to avoid it was turning off the AC and turning the blower on high just a couple of miles before getting home or work, or after any long trip for that matter. that little bit of time allowed the coils to dry out a bit, and generally the air stayed cool enough for the final few minutes of the drive. Yeah its and extra step but it did work...