What prompts the fan to come on?

rnm37

rnm37

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Hi all,

Have a 2013 1.6tdi SE A3, drive around 300-350 miles a week on mainly motorways and A-roads. Every so often when I get out my car after a longish journey (my commute is 50mins) the cooling fan comes on full belt and runs for around 5-10 minutes. This often happens after fairly sedate drives returning 65mpg+.

Is this the car trying to do a DPF regen or something else? Can't quite work out what driving conditions prompt it.

Cheers.
 
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I'd say it is the DPF regen cycle. Observed the same trait on my car as well. You will also notice that the idling speed when stationary will be slightly higher than normal (around 1000 rpm) compared to the "normal" 850 rpm.
 
Yep DPF regen, mine used to come on just as i was at the end of my journey......****** annoying.
 
My old petrol 3.2 use to run the fan for a while after turned off regularly Not linked to journey length either


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On a modern Audi diesel its because the car was stopped whilst the car was in the middle of an activated regen - it should complete the regen when next started. This shouldn't really be a regular occurrence on your mileage as the car should be conducting natural regens during the journey with the prolonged periods of exhaust heat simply burning off the soot on a "drive-as you go" basis without the need for and activated regen. I've had my car for 3 years and my mileage is not as high as yours and I've noticed this occurrence just twice.
 
Retroman said:
On a modern Audi diesel its because the car was stopped whilst the car was in the middle of an activated regen - it should complete the regen when next started. This shouldn't really be a regular occurrence on your mileage as the car should be conducting natural regens during the journey with the prolonged periods of exhaust heat simply burning off the soot on a "drive-as you go" basis without the need for and activated regen. I've had my car for 3 years and my mileage is not as high as yours and I've noticed this occurrence just twice.
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Yeah it's very irregular, maybe once every couple of months if that.
 
My trips happen to be quite short due to where I live and hence I encounter this event every now and then. Just yesterday I had a DPF regen failure. The car was regenerating on Sunday but again the trips where short. On Monday I encountered a lot of slow moving traffic and knew that the regen was going on and suddenly I got this fault. I could not rev the car and go at speed. After 10 minutes the warning cleared. Once I was past all the traffic I could drive in a spirited way to help clean the DPF. Let's say I was not amused with the warning especially considering that the car is only 9 months old and only has 5000 miles on the clock, however I have to live with it and it was a risk I was ready to take as I needed a diesel car due to the amount of mileage i do every year.
 
The correct answer is.

A DPF is a diesel particulate filter. An electrical filter inside the exhaust. This collects sutt before it enters the environment. What this does it when it builds up it increases the pressure going through the filter from the gasses, the filter has a sensor that sits above the filter which registers the pressure of gasses passing. Once it reaches the correct pressure it then begins what we call a regeneration cycle which heats the filter up to 600degrees to burn off the sutt for a second time before it releases into the environment in order to make the vehicle emissions 'cleaner'. This is perfectly normal and will more than likely happen every time you drive the vehicle. If you're on the motorway you wont notice it and the symptoms will be less noticeable as it's automatically regenerating and the vehicle doesn't have to force itself to meet the requirements.

The symptoms are, higher fuel consumption, higher idle revs, nosier engine, and a burning smell from underneath the car.

What's probably happening is it regenerates on your commute which is brilliant, it's finished the regeneration before you stop the vehicle but still needs to keep the fans on for around 10 minutes to cool down the half already cooled down DPF filter.

If you stop driving during a regeneration that's not an issue unless is happens routinely, but the filter would still be at 600degrees and the fans would run for 30minutes for safety reasons.

Don't worry about it unless a light comes on. Drive it as you do.

Hope this helps :)
 
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@Bitsieee should I therefore worry when my light came on yesterday? The error did clear out during driving and the car is running normally, idle speed at around 850rpm on neutral and fans are off.
 
Are you certain it was the regeneration light came on? The car would only every lose power when it's in limp mode meaning either EML or Coil light would be on.

But the car does feel lumpy when regenerating
 
I'm very sure as I had a yellow warning saying DPF regeneration failure, however as I said it cleared itself after 10 or 15 minutes. I'll monitor the performance of the car over the coming days. Usually due to the nature of the traffic in Malta the DPF regen occurs every 150 -200 miles
 
Ahh ok, yeah I wouldn't worry too much unless the light comes back on
 
Bitzieee said:
The correct answer is.

What's probably happening is it regenerates on your commute which is brilliant, it's finished the regeneration before you stop the vehicle but still needs to keep the fans on for around 10 minutes to cool down the half already cooled down DPF filter.

If you stop driving during a regeneration that's not an issue unless is happens routinely, but the filter would still be at 600degrees and the fans would run for 30minutes for safety reasons.

Don't worry about it unless a light comes on. Drive it as you do.

Hope this helps :)
Click to expand...

Bitziee,
Loads of different posts on this issue but looking at the scenario's you comment on, surely if the re gen is finished the fans will stay on until the engine reaches the lower temp level set by the manufacturer. (Could be ten mins or simply two mins to achieve ).
The point I am making is that there is no set time for the fans as lots of variables to consider during the re gen and people may think they have a fault if their fans are operating differently from the your times you quote.

Bitzieee said:
Are you certain it was the regeneration light came on? The car would only every lose power when it's in limp mode meaning either EML or Coil light would be on. But the car does feel lumpy when regenerating
Click to expand...

My last A4 TDi dpf orange light used to come on to indicate that it needed a re gen if it did not complete one during normal driving, the manual told me what to do, ie it specified the revs for a specified time to re gen it and clear the warning light. IMO the way that @lawrence-ellul car indicates is normal (not a failure) given his driving/journey and requires that action (unless a red light comes on with it which indicates a forced re gen is needed).
 
traindweller said:
Bitziee,
Loads of different posts on this issue but looking at the scenario's you comment on, surely if the re gen is finished the fans will stay on until the engine reaches the lower temp level set by the manufacturer. (Could be ten mins or simply two mins to achieve ).
The point I am making is that there is no set time for the fans as lots of variables to consider during the re gen and people may think they have a fault if their fans are operating differently from the your times you quote.



My last A4 TDi dpf orange light used to come on to indicate that it needed a re gen if it did not complete one during normal driving, the manual told me what to do, ie it specified the revs for a specified time to re gen it and clear the warning light. IMO the way that @lawrence-ellul car indicates is normal (not a failure) given his driving/journey and requires that action (unless a red light comes on with it which indicates a forced re gen is needed).
Click to expand...

Sorry i ‘presumed’ you lot would gather that i was speculating at the ‘precise times’ they would just a rough guess but yes they do change.

However it’s a maximum of 30 minutes even in if engines stopped mid regen. Anything longer than 30 minutes then we would start to worry.

Yes more than likely, i was just double checking it was the regen warning that came on as the vehicle ‘lost power’.

Not entirely sure what you’re getting at with your response though i just wanted to give my professional overview. If you’re passing by Wigan Volkswagen any time i could show you some brilliant videos on it which will explain it better than i ever could, although i’m not far off word for word these days haha


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Personally I believe that some over-state the problems with DPFs. I've not had problems and I know many diesel owners (some potter about on short trips) and none of them have had DPF issues. The internet tends to give a biased sample when it comes to problems as the majority, who have no problems, don't tend to go online and talk about it. It was the same when catalytic converters were first fitted - doom and gloom from some quarters - now nobody gives them a second thought.
 
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Retroman said:
Personally I believe that some over-state the problems with DPFs. I've not had problems and I know many diesel owners (some potter about on short trips) and none of them have had DPF issues. The internet tends to give a biased sample when it comes to problems as the majority, who have no problems, don't tend to go online and talk about it. It was the same when catalytic converters were first fitted - doom and gloom from some quarters - now nobody gives them a second thought.
Click to expand...

Stop start fits into this category of ‘fitted features and components everyone thinks has a negative effect on the car because the idea 20 years ago was ridiculous but since then the whole industry has changed and it works perfectly and causes no harm only benefits if you learn to work with it’


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