# Musty smell when recirculation is on - clean A/C evaporator?



## sean_m (Oct 6, 2010)

There is a musty smell when recirculation is on, but it's fine normally. It would seem there is some low level of buildup that isn't noticeable as long as fresh air is diluting the odor. Is there a recommended chemical and procedure for cleaning the evaporator and ducts?


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## Tiger0002 (Apr 23, 2013)

There is a foaming evaporator cleaning product to take care of that... basically they inject foam into the evaporator chamber via the drain tube... the foaming action will saturate the entire chamber and clean up everything... This is done with the car off... after elapsed time... they turn on the car and AC so the condensate drains the cleaner out of the chamber. 

But before you do this, I highly recommends you change your cabin air filters first.


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## PanEuropean (Nov 3, 2001)

Tiger0002 said:


> But before you do this, I highly recommends you change your cabin air filters first.


 Stan: 

Please be judicious when making suggestions to others. Sean specifically stated that the musty smell was present when the air recirculation feature is active. If the air recirculation feature is active, then the vehicle is not drawing any air in through the cabin air filters. 

An occasional highly accurate and carefully thought out reply is much better than a large quantity of poorly thought out responses. 

Michael


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## Paximus (Aug 26, 2011)

I don't think I would want foam to penetrate the 15 flap motor assemblies in my car's HVAC unit. I think the repair costs could be on the way to writing the car off. 

There are professional ozone treatments that might work (although ozone can make plastics more brittle), or I seem to remember that VW has posted a recommended procedure to deal with this problem on erwin.volkswagen.de. Next time I log on there I'll see if my memory is playing tricks or not. 

Chris


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## Tiger0002 (Apr 23, 2013)

Even with air recirculation ON, the exterior air flap is never 100% shut. There is always new air coming in. Are you saying the cabin filter is only for air intake? Most cabin filter filters the interior air that are sucked into fan and then through the evaporator. 

Chris brought up interesting info... 15 flaps by the evaporator? I can only imagine the air recirculation flap and mixing flap within close proximity. The foam doesn't penetrate that far into the air ducts. But it is an issue to be considered. 

Lastly, when you got musty smell in the car, you do need to clean the carpet... and look to see if you got water leakage to inside the car that will ruin your Kessy unit.


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## Paximus (Aug 26, 2011)

Here's what VW have to say about the air filters. I suppose it might inform the discussion!  

Chris 


*Function of dust and pollen filter with activated charcoal filter insert * 



A dust and pollen filter [_actually, two_] with activated charcoal filter insert is installed together with the air quality sensor. 

The activated charcoal filter insert still has the task of filtering out dust and pollen. But it can also filter harmful gasses such as ozone, benzene, nitrogen dioxide etc. out of the air flow. 

The task of the activated charcoal is to absorb impurities from the air flow until the fresh air flap is closed and the air conditioning system is operating in air recirculation mode. If the “automatic air recirculation” function is selected, the Climatronic control unit -J255- switches from fresh air to air recirculation mode as soon as the air quality sensor detects gaseous impurities in the ambient air. 

The activated charcoal layer in the dust and pollen filter reacts with noxious substances in the air in different ways: 
- Certain noxious substances are stored permanently in the activated charcoal layer. 
- Others are converted into harmless compounds in a manner similar to that of a catalytic converter. 
- For the remaining substances, the activated charcoal functions like a condenser. As noxious substances increase, initially they are stored until a certain level of saturation is achieved. As the portion of noxious substances in the air decreases, the activated charcoal layer gradually releases the particles. 

Because the activated charcoal layer permanently stores part of the noxious substances, renewing the dust and pollen filter before the prescribed renewal period would be advantageous, if: 
- the vehicle is driven in areas with heavy air pollution. 
- the vehicle is driven mainly with the “automatic recirculation mode” switched off. 
- the vehicle is not equipped with an air quality sensor and consequently has no “automatic recirculation mode”. 

On vehicles with air quality sensor, the air conditioning system should generally be operated with the “automatic recirculation mode” activated. However, if it is necessary or desired to switch the function off, the following should be observed: 
-The activated charcoal layer in the dust and pollen filter will become saturated after a certain period of time. 
-A saturated filter is not capable of absorbing any more noxious substances, and these will flow unrestricted into the vehicle. 

The main task of the dust and pollen filter and the air quality sensor -G238- is to prevent peak levels of pollution from entering the passenger compartment of the vehicle. To this end, the following should be observed: 
-If the vehicle is being driven in an area with relatively clean air (with low levels of noxious substances), switching from fresh air to air recirculation mode is actuated at a different point in time than in an area with a high level of pollution (e.g. industrial area). 
-The switch from fresh air to air recirculation occurs independently of the base level of pollution whenever the pollution level increases (e.g. when driving through a cloud of exhaust soot).


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## sean_m (Oct 6, 2010)

I did check my cabin air filters when I first noticed the problem, which were replaced at the last service interval. In any case, they are still clean and have no odor of their own. As Chris mentions, the high complexity of the air distribution system is why I haven't tried any conventional cleaning products. 

I ended up finding a relatively recent TB, 87 07 14, for cleaning the system 
http://www.clubtouareg.com/forums/attachment.php?attachmentid=2817&d=1192329863 

which indicates the use of an ultrasonic atomizer that discharges cleaning vapor into the interior intakes in recirculate mode 

I also found older info in ELSA: 



> Evaporator, Spraying with Pressure Cup Gun and Spray Nozzle -VAG 1538-
> 
> Spray off the evaporator directly with Contra Sept using a spray nozzle (approximately 10 bar (145 psi)) Contra Sept neutralizes microbes and bacteria directly on the evaporator.
> 
> ...


 indicating cleaning fluid should be sprayed directly on the evaporator, which is a pain to access and requires removing the windshield wipers, air intake shroud with the airflow doors, and the fan assembly. More trouble than the problem is worth at the moment.


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## Paximus (Aug 26, 2011)

Thanks for the information, Sean. 

As a postscript, it could be worth checking that the evaporator drains are freely open. This would be partly for the musty smell and partly, as Stan says, to protect the KESSY if they are, in fact, becoming blocked for some reason and could freeze up some dark winter night. 

Chris


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## Tiger0002 (Apr 23, 2013)

That is an interesting cleaning process... basically fogging the entire duct system with AC off (Econ mode on) and low fan speed. 

I wonder how many dealer has this machine.


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## PanEuropean (Nov 3, 2001)

Tiger0002 said:


> Are you saying the cabin filter is only for air intake? Most cabin filter filters the interior air that are sucked into fan and then through the evaporator.


 On the Phaeton, the two air filters (pollen filters) only filter new, unconditioned air that is brought in from the outside. It is impossible for these two filters to filter any air that is already inside the cabin (in other words, to filter recirculated air). 

Michael


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## nataliewashington (Dec 16, 2013)

You have to clean the ac properly. There are lot of mobile emergency ac repair company which will clean or maintain your ac immediately. Just make a call and you are good to go.


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## PanEuropean (Nov 3, 2001)

sean_m said:


> There is a musty smell when recirculation is on, but it's fine normally. It would seem there is some low level of buildup that isn't noticeable as long as fresh air is diluting the odor. Is there a recommended chemical and procedure for cleaning the evaporator and ducts?


Hi Sean:

There are two possible causes that I can think of for a musty smell when recirculating cabin air: One is that there is some kind of contaminant on the evaporator coil, and the other is that there is some kind of contaminant in the evaporator coil drain pan.

If the contaminant is on the evaporator coil itself, then you will need to clean the coil. How to do this has already been discussed (above) in this thread.

On the other hand, if the smell is caused by a contaminant in the evaporator coil drain pan, it is possible that you could solve the problem (get rid of the smell) by making sure that the two drain outlets for the air conditioner assembly are not blocked. In other words, you want to confirm that any liquid (typically condensation that forms on the evaporator) can easily and quickly drain out of the car onto the ground below.

Have a look at this discussion, it explains where the drain outlets for the evaporator are, and how to ensure that they are unobstructed: Accessing the evaporator drain / Liquid "sloshing" sound in cabin.

Michael


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