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  1. #1
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    Engine drag from AC?

    A3 2.0 SE TDi 170 2008 model. Auto climate control.

    As soon as I switch on my AC unit The drag on the engine is enough to make it run roughly and appear to lack power. It certainly is nowhere near as smooth to drive with it switched on.

    It makes no difference what temperature is set, the drag is the same.

    With all other cars I have owned with AC fitted, there has been no noticeable change at all when AC is switched on.

    Is this common or normal, or do I have a fault somewhere? There are no fault codes showing.

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  3. #2
    Ash187's Avatar
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    i think its common for a slight bit of power loss when the Ac is on, but it doesnt feel rough in mine when i switch it on
    A3 Sportback 2.0TDI
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  4. #3
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    I seem to remember when your idle, and you switch AC on the revs dip briefly, thus changing engine note, but power wise I think it's steals something like 5-10% of yours cars power.

    its a thirsty bit of equipment!
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  5. #4
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    Bit different but my old Peugeot 206 2004 plate used to drag slightly when AC was switched on...
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  6. #5
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    It is normal to feel a chang in the way the engine runs when you switch on the AC but with 170 HP and at least 350NM of torque this shouldn't be THAT noticeable.
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  7. #6
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    I have noticed this now the weather is warmer and the AC unit runs.

    Does anyone know if a AC recharge/regass will help reduce the drag?
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  8. #7
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    Quote Originally Posted by Johnny Bravo View Post
    It is normal to feel a chang in the way the engine runs when you switch on the AC but with 170 HP and at least 350NM of torque this shouldn't be THAT noticeable.
    I can barely detect any change with mine - before remap or after.

  9. #8
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    Never noticed this on any of my three A3s - I'd get it looked at.
    Daytona Grey Audi A3 2.0TDI 150 S-Line with Tech Pack, Comfort Pack, Interior Light Pack, Alcantara/Leather seats, B&O sound, DAB radio, Folding/dimming mirrors

  10. #9
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    Don't notice it on my S3, but my modified Subaru was a pig to drive with it on! Changed the pedal feel big time and was noticeable.
    2011 61 plate S3 SB BE DSG - Shark Stage 1 + DSG

  11. #10
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    Quote Originally Posted by Glyn E View Post
    A3 2.0 SE TDi 170 2008 model. Auto climate control.

    As soon as I switch on my AC unit The drag on the engine is enough to make it run roughly and appear to lack power. It certainly is nowhere near as smooth to drive with it switched on.

    It makes no difference what temperature is set, the drag is the same.

    With all other cars I have owned with AC fitted, there has been no noticeable change at all when AC is switched on.

    Is this common or normal, or do I have a fault somewhere? There are no fault codes showing.
    Mine feels different with ac on really sluggish
    A3 Sportback 2.0 TFSI S-Line Quattro Stage 1 Tune it up - Lowestoft Custom Remap- 6187 RPM developing 260 bhp 279lbs ft Akoya Silver, Roof rails, Black heated Vienna Leather, Bose upgrade, Bluetooth

  12. #11
    cjsuk's Avatar
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    Most cars ive had with aircon on have run rough on idle, and taken power. It depends how rough and how much power loss is, and even if the aircon was really shafted I cant see how it can make more of a power loss or rougher idle.

  13. #12
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    The thing I don't understand is, how do you know when the aircon is "on"?

    With climate control, whilst you can disable the aircon compressor via the ECON or AC button, if you leave it to its own devices, then it's up to the climate control system whether the compressor is needed or not. In this situation, I've not once noticed any detectable change in performance or responsiveness that would indicate whether the compressor is engaged or not.
    Daytona Grey Audi A3 2.0TDI 150 S-Line with Tech Pack, Comfort Pack, Interior Light Pack, Alcantara/Leather seats, B&O sound, DAB radio, Folding/dimming mirrors

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    Quote Originally Posted by Vertigo1 View Post
    The thing I don't understand is, how do you know when the aircon is "on"?

    With climate control, whilst you can disable the aircon compressor via the ECON or AC button, if you leave it to its own devices, then it's up to the climate control system whether the compressor is needed or not. In this situation, I've not once noticed any detectable change in performance or responsiveness that would indicate whether the compressor is engaged or not.
    Econ turns AC off completely, atleast it does on mine.

  15. #14
    cjsuk's Avatar
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    I have a bit of a noisy compressor so I know mine is on, if I leave the climate control on auto, the compressor is allways on no matter weather its its got to its temperature or not its only off when I press off or econ, so if you have it on auto all the time, you wont notice a difference as its allways on.

  16. #15
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    Quote Originally Posted by cjsuk View Post
    I have a bit of a noisy compressor so I know mine is on, if I leave the climate control on auto, the compressor is allways on no matter weather its its got to its temperature or not its only off when I press off or econ, so if you have it on auto all the time, you wont notice a difference as its allways on.
    It shouldn't be running all the time unless you have the temp set really low on a warm day... It should cut in and out.
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  17. #16
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    Quote Originally Posted by Minstadave View Post
    Econ turns AC off completely, atleast it does on mine.
    I know, that's what I said. What I mean is, unless you disable it completely via the ECON or AC button, there's no way to know whether the compressor is actually on as it's up to the climate to decide and there's no indicator to tell you.
    Daytona Grey Audi A3 2.0TDI 150 S-Line with Tech Pack, Comfort Pack, Interior Light Pack, Alcantara/Leather seats, B&O sound, DAB radio, Folding/dimming mirrors

  18. #17
    964kevin's Avatar
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    Makes no diffeence to mine, though you can see how much fuel it takes to run on the DIS, about 1/12th gallon per hour if memory serves.

    K

  19. #18
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    When I turn the AC on my 2010 S3 the revs on idle pick up ever so slightly, no noticeable difference on running though

 

 

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