Questions for 2011 and similar year models on the subject points - So- Two questions, after hours of searching revealed nothing. One day- (months and months ago), I took in ...

So- Two questions, after hours of searching revealed nothing.

One day- (months and months ago), I took in my new truck to the dealer because when the A/C was on, it would get musty smelling. I know there's no more cabin air filters going on a decade now, but I thought it's a new 2011 Silverado (maybe a year old at that point), nothing should be wrong. I run the A/C all the time, and this was back on recirc to avoid nasty outdoor odors (I have a tendency to be sensitive, especially around smoggers and smokers).. so it didn't go for a long time without being used- and the Chevy Service manager asked if I ran recirc a lot and after getting a yes from me, said- Don't use it. Because it's used, it doesn't get to air out and causes the musty smell. They could flush the system for a cost- (eff that) and not have a guarantee that the smell would return. Or I could run it, and then swap to reg A/C intake to bring outside air in a few minutes before I get to where I'm going to dry the lines out. I do a lot of stop and go back and forth 5-10 minute runs so that's an unfeasible idea. Kind of makes me wonder what the point is of the recirc if it freezes out the lines and blows musty smells after awhile. I have switched to just venting A/C most of the time, and on the hot days an occasional recirc or when I pass by someone smoking, so the smell has abated but does this sound familiar to anyone else- about the musty smells?

Second question- Has there been any updates on the aftermarket mods- or has anyone done a retrofit to get some sort of cabin air filter on a 2011? I saw someone did a retrofit kit for a 2003 but that body style is drastically different and I wasn't sure if there was any updates anywhere... Searches revealed nothing- although I could have looked up the wrong terms. I just landed on a lot of 2011 postings.

The reason it was possible on the GMT800 series is that they didn't change the heater box other than to seal up the opening where the cabin air filters used to go. All you had to do was cut out the slot and fab an L-shaped bracket (simplified) to retrofit the cabin air filters. On the newer style I'm not sure there's even a place to accept a filter.

I run my ac on nothing but recirculate and I have an 09 year model and haven't had the first musty smell at all....

someone posted in another thread about a diy cabin filter that he made out of a motorcycle battery box. it can be done with the right ingenuity

Musty smell is probably the bacteria that grows on the core due to moist air. I'd have to look it up and don't have time, but most GM vehicles had a program internal to the BCM to turn on an afterblow feature that ran the fan after shutdown for a few minutes to help dry out the system to prevent the bacteria from growing. The A/C air filter was not designed to stop the bacteria it was just a filter to filter dirt out of the AC system.

^^^^^^^^^^
Retg hit the nail on the head. Gm had issues in the past with that my friends Saturn the air blower would run after shut down for a min with outside air to dry it out.

Filter help a little. But I also get it on my sons civic once in a whirl that car has a in cab filter and my wife's Acura also gets it once in a while.
In Vegas we run the a/c almost 6 months straight .the time we notice the smell is on humid days. But running outside air for a bit when you get the smell really helps.

From the GM service manual:

Eliminating Air Conditioning Odor
Odors may be emitted from the air conditioning system primarily at start up in hot, humid climates. The following conditions may cause the odor:

• Debris is present in the HVAC module.

• Microbial growth on the evaporator core

When the blower motor fan is turned on, the microbial growth may release an unpleasant musty odor into the passenger compartment. To remove odors of this type, the microbial growth must be eliminated. Perform the following procedure:

Deodorize the evaporator core using Deodorizing Aerosol Kit.

Perform the following steps in order to deodorize the A/C system:

•Ensure that the plenum which draws outside air into the HVAC module is clear of debris.
•Disable the A/C compressor clutch operation by disconnecting the clutch coil electrical connector.
•Dry the evaporator core by performing the following steps:
3.1. Start the engine.

3.2. Select the warmest temperature setting.

3.3. Select the recirculation mode.

3.4. Run the blower motor on high for 10 minutes.

•Locate an area in the air conditioning duct between the blower motor and the evaporator core downstream of the blower motor.
•Drill a 3.175 mm (0.125 in) hole where the hole will not interfere with or damage the following components:
• The blower motor

• The evaporator core

• Any other operating part the of system

•Wear safety goggles and latex gloves in order to perform the following actions:
6.1. Select the maximum blower speed.

6.2. Insert the deodorizer extension tube into the hole to the mark on the extension tube.

6.3. Use short spray bursts and vary the direction of spray for a 2-3 minute period of time.

•Shut the engine OFF. Allow the vehicle to sit for 3-5 minutes.
•Seal the 3.175 mm (0.125 in) hole with body sealer or RTV gasket compound.
•Start the engine.
•Operate the blower motor on high for 15-20 minutes to dry.
•Reconnect the A/C compressor clutch coil electrical connector.
•Verify proper clutch operation.


You can call a dealer and see if, on your model year vehicle, there is an afterblow function that they can turn on via the Tech 2....

From the service manual:
Afterblow Enabling
The afterblow mode can be enabled using the scan tool. The afterblow mode allows the blower motor to operate after the engine has been turned off. This operation of the blower motor dries the evaporator core, which reduces the amount of microbial growth which can create undesirable odors.

Use the following procedure in order to enable the afterblow mode:

•Connect the Scan Tool.
•Turn ON the ignition, with the engine OFF.
•Build the vehicle with the scan tool.
•Select HVAC Control Module
•Select Module Setup.
•Select Afterblow Option.
•Upon selecting the afterblow option a asterix will appear next to the word afterblow meaning the function is enabled.
•Select the save option in the lower left of the screen.
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.

^Great info!