I have that musty smell when first turning on the aircon. I have replaced the cabin filter with the most expensive MAN filter that is available. Makes no difference. Car is immaculate inside and out, non smoker, no pets. I was looking at the foam pipe cleaner cans that you put in the vents, but I cannot find a decent video on how to do it for my car. Some say use Dettol antibacterial spray in the outside vents (where are they?) and run the aircon on full blower cold (not recirc) for 10 minutes. They also say take out the cabin filter and spray inside too as that's where the condenser is. It was a pain replacing the cabin filter as it has a small slot under the drivers seat. I don't even know how you can see the condensor from there. If I get the foam version, how do I know if I am spraying it on the condensor if I take out the cabin filter? Any help with pics/vids would be much appreciated!

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"I have that musty smell when first turning on the aircon". There lies your problem, the aircon should always be on,it is to condition the air regardless of temperature.

Get a AC cleaner from your nearest Halfords of local motor factors and then use that, they are anti bacterial and anti fungal (usually the cause of a bad smell) the instructions will be something along the lines of move passenger seat all the way forward, lean it forward, latch the spray, put it behind the passenger seat with AC on full blast and resurc, leave it till the spray has run out, then open all doors and windows, turn car off and let air

Just now, deandeandean said:

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"I have that musty smell when first turning on the aircon". There lies your problem, the aircon should always be on,it is to condition the air regardless of temperature.

Not true, it's actually very bad for you to always have a on as it dries the air out

Air-Con Bomb Citrus - Bilt Hamber

Well there's no musty smell in my car.

14 hours ago, GIXXER1000 said:

I have replaced the cabin filter with the most expensive MAN filter that is available. Makes no difference.

Should have bought the WOMAN filter.  Can pay 20% less for that one. 

Ideally it's best to put the foam pipe directly up the AC condensate drain.  That's the only way you can be sure you're hitting the evaporator instead of the heater matrix.

Unfortunately, on the Mk7, the drain drop straight downwards from the bottom of the HVAC box, through the chassis, to drain above the exhaust heatshield.  Not easy to access.

If spraying Dettol or similar from outside then really the pollen filter needs to be removed first.  The spray will just get stuck in that otherwise.

8 hours ago, TomsFocus said:

Ideally it's best to put the foam pipe directly up the AC condensate drain.  That's the only way you can be sure you're hitting the evaporator instead of the heater matrix.

Unfortunately, on the Mk7, the drain drop straight downwards from the bottom of the HVAC box, through the chassis, to drain above the exhaust heatshield.  Not easy to access.

If spraying Dettol or similar from outside then really the pollen filter needs to be removed first.  The spray will just get stuck in that otherwise.

Thanks, I think using Dettol antibac through the exterior vents with the new pollen filter removed is probably the best (and cheapest) option for me. I would have liked to have used the pipe with foam in the condensate drain method, but you have confirmed my suspicion that this would be difficult on my car. Another poster suggested those air bombs, but I tried one in one of my previous cars and it did virtually nothing, waste of money. As you said, the smell is most likely mould from the evaporator, not in the vents and you need to target this as directly as possible.

On another car which had a slight smell, I had an aircon regas, and had the Pros do a 'bomb' at the same time.  It worked really really well.  Stopped the smell.  Sometimes you have to pay the Pros for a result.