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Punchy smell from air circulation after aircon is switch off

Discussion in 'New A3/S3 (8V Chassis)' started by Schizophonic, May 21, 2014.

  1. Schizophonic
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    Schizophonic Active Member

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    Over the past few days I've used my aircon briefly and when I switch it off and run the normal air circulation I get a punchy sour smell. Its like mold or something thing unpleasant. Any ideas how to best get rid of it?

    I wouldn't have thought my car being just a year old would have this problem. Is it worth investing money into one of those air fragrance bomb?
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  2. h5djr
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    h5djr Well-Known Member

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    The best answer is never to switch off the Air Con. I've always left mine on all year round and just set the temperature and let it react accordingly. Had it on all my cars (1 x Golf VR6 and 9 x A3) for the last 20 years and never had a problem.
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  3. Stephen C
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    Stephen C Active Member

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    This happened in my SEAT immediately after switching off AC, too. I think this is normal.

    My advice would be, in a car like an A3 with Climate Control, to just leave it on all the time.
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  4. oufc1976
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    oufc1976 Member

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    Leave Air Con on permenantly?

    Surely that will affect MPG?

    Also, can someone clarify something for me. In my head 'air con' means freezing cold.

    If you can have Air Con on and temp set to Hi, what actually does Air Con do?

    I've always thought of it as:

    Hot > Warm > Cold > Air Con
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  5. Stephen C
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    Stephen C Active Member

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    Probably takes a small amount off the MPG, yes. But depending on the temperature you've set, there will be varying loads on it. It also dehumidifies the air, which can be useful in winter (even when you want warm air) because it prevents condensation forming on the windows. It will only chill the air (by removing warm air) if you request this in the temperature you set.
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  6. oufc1976
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    oufc1976 Member

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    The things you learn! Cheers mate
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  7. mjcourtney
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    mjcourtney Well-Known Member

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    Modern air con systems (particularly climate control systems) are designed to be on for the majority of the time. It takes minimal load from the engine and helps to maintain levels of humidity and temperature in the cabin. Systems which aren't used often actually are at higher risk of failure due to the seals in the system drying out over time.

    Leave it in auto with the a/c on for best long term results (even in winter!).

    The smell you are experiencing is mould spores trapped in the cabin filter. Air con dries this out and stops the smell.

    Hope this helps
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  8. h5djr
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    h5djr Well-Known Member

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    Yes leaving the Air-Con on all the time may use a fraction more fuel, but basically only in hot weather when the clutch on the end of the compressor (the bit that enables cold air to be produced) is engaged. In colder weather this clutch disengages the compressor and it acts just like free running pulley. Opening the windows also uses more fuel because of the extra drag.

    If you have the 'climate control' the system will work to maintain the air temperature inside the car to the temperature you have set. If it's cold inside the warm air will be produced by the heater. If it hot inside then cold air will be produced by the system to cool it down until the set temperature is achieved. In each case the system will cut in and out as necessary to maintain the set temperature.
    If you set High or Low this will override the temperature setting and keep producing warm or cold air.

    If have 'manual' air conditioning then you have to decide if you want warm air or cold air depending on the interior temperature, and what you say about Hot > Warm > Cold > Air Con is about right. Having said that why anyone would buy a car like an A3 without electronic climate control is beyond me.
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  9. coolguy
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    coolguy Member

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    That's very interesting, I've always kept the air con off until I needed cold air (like the past few days).
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  10. veeeight
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    veeeight Well-Known Member

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    If you're really worried about the 2mpg extra consumption, press the AUTO button a second time, until "Eco" appears in the display.

    This widens the setpoint "band", and the climate control won't work as hard to maintain a narrow setpoint band.
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  11. cuke2u
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    cuke2u Well-Known Member

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    The vents need cleaning and disinfecting and you can get products specifically from Halfrads to do this...
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  12. 0B1001001
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    0B1001001 Active Member

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    Dammit - there you go reading the manual again :D
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  13. veeeight
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    veeeight Well-Known Member

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    Sorry :(

    :lmfao:
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  14. JohnnyM100
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    JohnnyM100 Active Member

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    Agree with Cuke2u that a disinfecting 'bomb' or equivalent would sort this. Dealers also have this too but don't know if it is available to buy other than during a service. A lot of short journeys with aircon can also accelerate the growth and smell.

    I don't have my aircon on all the time. I do make sure it is on when I need it (obviously) and also run at least once a week to keep the parts moving and seals lubricated.

    I do however switch aircon off when I am about 5mins from my destination. This allows the water in the condenser to drain and for it to dry out before I stop the engine. No dampness festering in the water condenser means no bacterial / mould growth and no smell.

    John.
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  15. cemerson
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    cemerson Well-Known Member

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    Another vote for 'on all the time' - did this with my old car too, but sometimes turned it off just to see the difference in fuel consumption. Barely noticeable. Modern systems are a lot more efficient than the older ones! Don't think I've yet turned the air con off in the A3...
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  16. sidibear
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    sidibear Looking for Zombies !! Staff Member Moderator

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    Mine is on all the time.
    If you do use a disinfecting bomb you will find that you get a kinda greasy film over the inside of your windows for a few days, easily wipes off but is annoying.
    The second time I did mine I opened all the vents and windows, put the fan on full and drove around for about 10 minutes, it was fine after that with no windows greasing.
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  17. Pickle1970
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    Pickle1970 Member

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    I think it's normal, i get it in my Honda Civic when i turn it off.

    Ps. I only ever use it when it's really hot as well. can't see the point of running it all the time when the temp inside the cabin is more than fine.
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  18. cuke2u
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    cuke2u Well-Known Member

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    There is a point or running the a/c often as otherwise the seals will dry out and start leaking if you don't use the air con, or climate control, for once a month for about 20 mins, however climate control should be left on all the time because that's what it is for. The smell isn't normal either, as part of any a/c service the vents and the evaporator are cleaned of any bacteria which causes it.
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  19. cemerson
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    cemerson Well-Known Member

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    Air con is more than just temperature.. You can still condition air and have it warm!
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  20. cuke2u
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    cuke2u Well-Known Member

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    Exactly...
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  21. oufc1976
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    oufc1976 Member

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    Great info. All the years I've had air con and I've only used it when I wanted to be cold.

    Will leave it on all the time now and probably put it in 'Eco'
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  22. ivicyrusivi
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    ivicyrusivi Member

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    If you've had the aircon on for any decent length of time then yes you tend to get the smell from stale water (condensation that forms).

    What I've always done is when I finish my journey and have had the ac on lots, I turn off ac and put the fans on full for a little bit to suck through some normal air and clear some of the condensation. Worked a treat on my A1 (Haven't had much use of the Ac on my s3 yet)

    Give it a go!
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  23. h5djr
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    h5djr Well-Known Member

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    As I and others have already said, just leave it on all the time. I don't do anything at all with mine and I forget I've even got it unless it very warm outside and lovely and cool in the car. Air Con is just that, Air Conditioning, not just Air Cooling.
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  24. ivicyrusivi
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    ivicyrusivi Member

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    Yea but in hot weather it's always cooling which can mean buildup of moisture... Flushing it through can help reduce the build up. Just give it a try if you get the weird smell often
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  25. h5djr
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    h5djr Well-Known Member

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    Been just leaving mine on all the time in eight A3s since 1998 and never ever had any bad smells. The Air Con system dries the air as well as changes the temperature.
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  26. ivicyrusivi
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    ivicyrusivi Member

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    I know it dries the air but the cool air and warm ambient air etc.... I dunno, just works for me in my other cars... Quick blast does it, nothing prolonged

    Edit: the smell I've got on occasion isn't really punchy, more of a very faint musty damp smell
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  27. cemerson
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    cemerson Well-Known Member

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    If it's a humid day and you do this, you risk introducing more moisture into the system than you had in the first place!

    Never had any of these strange smells that people are talking about so don't think it's necessary for me to try it really!
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  28. ivicyrusivi
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    ivicyrusivi Member

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    I meant for the op to give it a try :)

    Just saying what's worked for me in the past. My a1 and others with manual ac sometimes got a faint smell, I found that doing this helped. Like I said, I haven't had any issues with the auto ac in the s3 as of yet

    The way I see it, and I'm only speculating, is moisture in the air isn't really a problem unless it condenses from the very cool air, kinda like you can get on windows, which could cause drips and form a little collection of water. I guess that water and warmth especially when humid (like you mention) is ideal for bacteria to grow (causing a slight smell). Just applying a little science / my own common sense. But then again I may be completely wrong
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  29. Schizophonic
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    Schizophonic Active Member

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    Right I'll leave the air con on and see what my mpg will do. I'm always been conscious how much it will affect and how much fuel is used. At the moment my main priority is to get rid of the smell but I've taken on board the suggestions and will leave the air con on for a duration and see for myself what it does. Thanks all.
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  30. h5djr
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    h5djr Well-Known Member

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    Once the air goes through the dryer unit it not longer contains enough moisture to create any drips within the system. I very rarely have to switch on my heated rear windows because there is no moisture in the air to cause the window to steam up.
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  31. JohnnyM100
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    JohnnyM100 Active Member

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    True Dave but sounds like you change your cars for new every 2 years before it has a chance to build up properly.

    I keep my cars for a lot longer (11 years last one) and using my method of switching off aircon for last few minutes of journey, I only got the smell once. If my approach was flawed and it was going to build up at all then it would have done so after that length of time.

    Clearly 2 schools of thought on this one so agree to disagree?

    John.
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  32. ivicyrusivi
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    ivicyrusivi Member

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    Ahh sry Johnny.... Just saw ur original post, much better explanation then mine :)
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  33. Daz Auto
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    Daz Auto Member

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    Had to do a little research on this. Correct me if I am wrong...

    The clutch is simply used to match the speed of the compressor to the fan belt. With manual A/C or automatic climate control, the compressor is either on or off. If manual A/C or CC are switched on then the compressor is always running producing cold/dry air (Except for ECO mode). My last car had manual A/C. My current car has automatic Climate Control. Neither of them misted up in the middle of the winter when I drove home from the gym.

    The flow of warm air is used control the temperature inside the car. Climate Control simple uses sensors to do this automatically.

    I never had a problem setting a comfortable temperature with manual A/C.

    The main advantage I find with Climate Control is dual zone. My wife has the uncanny ability to be the opposite of the ambient temperature. If it is hot, she is cold. If it is cold, she is hot. Sometimes she even has her side of the car set so high that I have to turn my side down!
    Last edited: May 23, 2014
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  34. h5djr
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    h5djr Well-Known Member

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    You are probably quite correct. The clutch unit on the compressor dis-engaging when cool air was not being requested was a feature on the aftermarket system I had fitted to my Golf VR6 back in 1994. Things may well have changed since then including the actual compressors becoming a lot more efficient.

    If anyone is bothered about the extra fuel that may be used perhaps they should run the system in "eco" mode as suggested in the Owner's Manual. Personally if I was that concerned about fuel consumption I would not have bought a 184 quattro.
    #34
  35. cuke2u
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    cuke2u Well-Known Member

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    I think that auto express once did some mpg tests on a astra, cough, and they found that the air con made a difference. Yes all compressors have had clutches on them even before 1994 and the more modern ones are of a low load type as well...
    #35
  36. ddscot
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    ddscot Member

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    Last car was an Astra 2006 and I didn't like driving it with AC on except on the motorway (caused the clutch to act heavy around town due to the compressor being engaged and the car idles faster) don't think it ever worked right anyway as I bought it 3 years old and that part of the system had no doubt never been serviced like a lot of used cars, it is a good idea to run it occasionally to circulate the oil and keep bacteria from breeding in the evaporator though (legionnaires is a nasty illness and for the same reason always use screenwash additive)

    Common problem on the VX was the condenser rad would rust at the bottom and separate causing gas escape, then no pressure equals no ac, quite dear to fix so lots of people don't bother.

    Best AC I ever had was on a 2005 focus zetec climate, I swear the vents started to form ice on that one and left you with a sore face after a while shivering.
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