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Discussion Starter · #1 ·
Hi, I’ve tried searching but couldn’t find a similar thread on this issue so I’m hoping somebody might have a suggestion.

Our 2011 Audi A1 TDI has developed an issue where there’s a very noticeable knocking noise when driving over bumpy road surfaces. The strange thing is that the problem is significantly worse when the interior heater fan is switched on (not AC, just the fan).
When the fan is off the problem is barely noticeable but with the fan on the knocking is so bad it feels like driving with broken suspension.

Any ideas would be very welcome.
Thanks
 

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2014 A1 Sportback 1.4 TFSI Contrast Line +
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Many times, noises when driving on bumpy roads is down to worn drop link bushes which are usually a simple fix (but can be expensive depending on parts prices).
However if this is related to the ventilation fan, maybe there is something loose in the heater matrix/box.... if you turn the fan off completely does the noise go away or reduce significantly? (hard to know what you mean by "barely noticeable"). When the car is parked, if you try "bouncing" the front corners is there any noise, because this would be a clue that the drop links or other part of the front suspension is the cause?
 

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Discussion Starter · #3 ·
Many times, noises when driving on bumpy roads is down to worn drop link bushes which are usually a simple fix (but can be expensive depending on parts prices).
However if this is related to the ventilation fan, maybe there is something loose in the heater matrix/box.... if you turn the fan off completely does the noise go away or reduce significantly? (hard to know what you mean by "barely noticeable"). When the car is parked, if you try "bouncing" the front corners is there any noise, because this would be a clue that the drop links or other part of the front suspension is the cause?
Thanks for your reply, so the knocking noise reduces significantly when the heater fan is switched off (not sure it goes entirely but it is at least 90% better when the fan is turned off). I think the heater matrix could be where the problem lies as you suggested. Another issue I forgot to mention (which maybe related) is that the car doesn't get up to full/normal temperature anymore (it stops at about 80c, again could that point to the heater matrix?).
 

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2014 A1 Sportback 1.4 TFSI Contrast Line +
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May be hard to tell but does it sound like the noise is coming from inside the car's cabin? If the engine temperature gauge isn't moving to normal, that is probably an issue with the thermostat and unrelated to the knocking.

Have you had the fault codes read by a garage or a friend with a code-reader?
 
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