S40 (New) AC : - Mildew smell but.... - Page 2

janusz · Jun 7th, 2014, 16:10

No sunroof here. The smell appears only when the aircon is on. Dealer says they have refreshed/cleaned the aircon so problem lies elsewhere and obviously they can help but an hour of labour costs...bla bla bla....
Perhaps one of you has a clue what could be the culprit:
When I switch the aircon on, there is no smell for few seconds, then I can hear a click coming from the engine bay and smell appears straight away. It is still there even when the aircon light is off (so no cold air is blowing). So frankly speaking there is no difference with or without the aircon. "Multi filter" was replaced 3 months ago during service at different dealer.
Any ideas? I am thinking about carbon pollen filter and "spray blast" cleaner - my concern is that problem does not sit with pollen filter but somewhere in the engine bay where the air enters aircon system.
Any help would be appreciated.

Weejada77 · Jul 4th, 2014, 13:23

I have exactly the same problem now. So I am watching and hoping that someone can give us a solution to this which is not too expensive??!!

Welton · Jul 4th, 2014, 16:46

This is strange as the smell would usually vanish with the a/c on. The bacteria only release an odor at ambient-type temperatures with the a/c off. With the dealer saying the problem is 'elsewhere' that only really leaves 'something' in the car that smells (no offence lol) it might be worth removing some of the plastics on the bulkhead to see the area where the air-inlet is which leads to the pollen filter housing see if anything's there? Switching the a/c on only actually brings the compressor on to deliver cooling refrigerant to the evaporator unit so shouldn't 'make a smell' on its own. Occasionally the climate will force full re-circulation in the cabin so blocks off outside air coming in. Play around with the recirc setting and see if you can recreate the problem - it might point to the smell source i.e. from inside the car or from the outside air inlet.

You may well have a bad case of bacteria in the climate control unit and the ducting. Maybe look further into ultrasonic cleaning, perhaps it wasn't done properly, all I know is that these cans that you 'let off' in the cabin are only really glorified air fresheners - I've had little success in the past with them. I'd also be inclined to maybe speak to a Mercedes dealer or similar for an air con treatment, they might be better placed to sort it, you never know.

Since the weather's hot today why not try running the system at MAX HEAT (with a/c off) and see if that kills most of the bacteria. You'll have to stand by the car though as it'll be *hot* in there.

Jun 7th, 2014, 16:10	#11
janusz Senior Member Last Online: Apr 11th, 2024 16:01 Join Date: Aug 2012 Location: London	No sunroof here. The smell appears only when the aircon is on. Dealer says they have refreshed/cleaned the aircon so problem lies elsewhere and obviously they can help but an hour of labour costs...bla bla bla.... Perhaps one of you has a clue what could be the culprit: When I switch the aircon on, there is no smell for few seconds, then I can hear a click coming from the engine bay and smell appears straight away. It is still there even when the aircon light is off (so no cold air is blowing). So frankly speaking there is no difference with or without the aircon. "Multi filter" was replaced 3 months ago during service at different dealer. Any ideas? I am thinking about carbon pollen filter and "spray blast" cleaner - my concern is that problem does not sit with pollen filter but somewhere in the engine bay where the air enters aircon system. Any help would be appreciated. __________________ XC60 SE Lux Nav D5 AWD

Jul 4th, 2014, 13:23	#12
Weejada77 Junior Member Last Online: Nov 25th, 2014 11:36 Join Date: Apr 2013 Location: Cambridge	I have exactly the same problem now. So I am watching and hoping that someone can give us a solution to this which is not too expensive??!! __________________ __________________________________________ V50 2.0D Manual 2004 (December) 54 Plate

Jul 4th, 2014, 16:46	#13
Welton Premier Member Last Online: Sep 14th, 2021 17:03 Join Date: Feb 2009 Location: Market Harborough	This is strange as the smell would usually vanish with the a/c on. The bacteria only release an odor at ambient-type temperatures with the a/c off. With the dealer saying the problem is 'elsewhere' that only really leaves 'something' in the car that smells (no offence lol) it might be worth removing some of the plastics on the bulkhead to see the area where the air-inlet is which leads to the pollen filter housing see if anything's there? Switching the a/c on only actually brings the compressor on to deliver cooling refrigerant to the evaporator unit so shouldn't 'make a smell' on its own. Occasionally the climate will force full re-circulation in the cabin so blocks off outside air coming in. Play around with the recirc setting and see if you can recreate the problem - it might point to the smell source i.e. from inside the car or from the outside air inlet. You may well have a bad case of bacteria in the climate control unit and the ducting. Maybe look further into ultrasonic cleaning, perhaps it wasn't done properly, all I know is that these cans that you 'let off' in the cabin are only really glorified air fresheners - I've had little success in the past with them. I'd also be inclined to maybe speak to a Mercedes dealer or similar for an air con treatment, they might be better placed to sort it, you never know. Since the weather's hot today why not try running the system at MAX HEAT (with a/c off) and see if that kills most of the bacteria. You'll have to stand by the car though as it'll be hot in there. __________________ 2005 S40 T5 SE - Manual. Bilstein B4's. (For Sale) 2010 Citroen C4 1.6 HDi (bizarre Gearbox model). 2010 Renault Twingo (refreshingly simple) 2018 Infiniti Q30 1.6T Business Executive (what's this button do?)

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