I don't think these trucks have a cabin air filter.

 

We don't have a filter. Water is getting trapped in the HVAC unit under the dash.

You might want to check if the drain is clear:
viewtopic.php?f=1&t=82456

I've heard that they make something you can spray into the HVAC intake to help kill the moldy stuff causing the smell. Not sure where to get it though.

 

I have a simular problem with smell for my 2007 Col. It smells when the vent fan is on. Using the ac usually stops it.

I tried a can of 1Z Klima-Cleaner WITHOUT success. It worked for less than a week.

 

GM makes an "afterblow module" that runs the HVAC blower intermittently when your truck is shut off and dries out the evaperator. I had one installed under warranty in my 2008 Colorado. It's a common problem and GM is aware of it.

 

You guys can also try to avoid this problem by running your heater full blast hot for like 10-15 secs after you've been using your a/c for a while. This will dry up most of the light condensation that accumilates on the evaporator under the dash that turns into mold overtime. Having a cabin airfilter i don't think will keep this from happening, it may reduce dust and some odors but the must is from surface mold on the evaporator.

Its true, GM does offer an afterblow module like cousincletus mentioned, but if your out of warranty your local dealership typically offers an air conditioning deoderizing service that usually involves drilling a small hole into the evaporator case and injecting some cleaner that turns into foam and gets into those really tight places like between the fins and evaporator core. Then they blow it out and add some deoderizing spray into the fresh air duct, etc etc.

These are a couple products we use at work, they're made by BG products. Im not really sure where you can buy this at but maybe seach around?

BG Frigi-Fresh®
BG Frigi-Fresh® is formulated to quickly and effectively eliminate foul, musty odors from automobile air conditioning systems. It kills mold, mildew and other odor-producing organisms that grow in the evaporator core and housing. Powerful deodorizers in BG Frigi-Fresh® keep the automobile interior smelling fresh and clean. EPA Reg. No. 44446-20-67145.
Part No. 7083

Part No. 708 Net Wt. 1 oz. (28.3 g)
Volume 1.12 fl. oz. (33.1 mL)
Net Wt. 5.5 oz. (156 g)
Volume 6.17 fl. oz. (182.6 mL)

BG Frigi-Clean®
Odors, bacteria, mold, spores, fungi, road grime, nicotine oils and debris accumulate in your car’s air conditioning evaporator. BG Frigi-Clean® restores heating/cooling efficiency and freshens interior air. It is a unique cleaning solution designed to quickly and effectively remove foul odors, bacteria, mold, spores, fungi, road grime, nicotine oils and debris that accumulate in your car’s air conditioning evaporator. BG Frigi-Clean® is injected directly into the evaporator case. It foams up to completely fill the evaporator core where it also blasts away bug parts, pet hair, nicotine residue and other garbage. BG Frigi-Clean® is biodegradable, non-toxic, non-corrosive.
Part No. 709 Net Wt. 7 oz. (198.4 g)
Volume 6.65 fl. oz. (197 mL)

 

What helped you guys with this problem? I have a 2007 model and it just started doing this. The weird thing is that it is intermittent but strong! So sometimes I get the odor really strong for a while and other times nothing. If I remove the cover to the blower motor and the motor as well could I get in there enough to physically clean the ac? Any thoughts?

 

Well I thought I had a weird moldy smell... then today I had a REALLY STRONG smell with smoke!! I have the same issue as many others with the blower motor resister and harness. Man this stinks (no pun intended).

 

Hello chrisquinn,

I am sorry to hear that you are experiencing an issue with your vehicle regarding strong smells. Can I be of assistance? I would be happy to see if there are any open recalls, concerns about warranty, or answer any general question you may have.

Jennifer T.
GM Customer Care

 

This is what my local dealer told me to do...

Roll down windows, run ac blower on high, fresh air not recirc. Spray lysol, lots of it, into the vent cowl between hood and windshield it will be pulled into the ac system and will kill the mold that is causing the odor.

I was advised to turn off the ac and run on fresh air for about the last minute of my drive to prevent this from recurring.

I have done this twice now, and it does work. I don't know of any easy way to get access to the evap coil to clean it, maybe through the blower opening, but even that is in a really awkward place... I think the lysol is about the best you can really do.

And yes i just did the wire harness and resistor on mine a couple weeks ago, what stupid problem... Relatively easy fix though. $78 in parts...

 

Hello, GM Customer service,

I to am also having the same problems. Can you check if I have any open warranties please. I have a 2005 Chevy colorado xtreme