Fan activating after short journey

[loz65]

I've got a new Audi A6 Avant Ultra S-tronic, which I've had for 4 months.

I've noticed that on a couple of occasions in the last week that the fan has remained on for around 5 or so minutes after I've turned off the engine, after only short journeys (less then 15 minutes and not caning it!). Whilst I appreciate that the fan will come on sometimes after a journey, should this happen in the above situations, when the weather is not exactly tropical!

[Lukenkarl]

Probably dpf regeneration, but wouldn't have thought it would do it twice in a week. I am not sure. A Vcds scan of soot level would give more information

[loz65]

Sorry, meant to add that on the second occasion this has happened (first time Wednesday, second time today), there was a distinct smell of engine as well!

[St3veM]

Deffo a DPF regen; you stopped the engine during the cycle so it will be hot hence the fans running post shutdown to cool the exhaust down.


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[loz65]

Thanks for the feedback - I do a lot of short journeys so is the best thing a blast up the motorway every week - how long for?

[St3veM]

I don't know the specifics on when the regen triggers but I would have thought a good 30 mins at 60mph + at 2k rpm+ should kick it off; feel free to correct me if I'm wrong folks.


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[Guest 2]

If you're only doing short journeys you should really be in a petrol.

Fans on is an early sign things will get worse if you continue your current driving style.

[loz65]

Oh dear, looks like I might have to sell then - oh well, only £3000 a month depreciation so far..... Unfortunately, Audi seem to think you only want a petrol if you're after mega BHP.

Seriously, will not taking it for a blast every week not resolve this?

[Guest 2]

You'd need at least 30-40mins @ 70mph in 4th gear if you're doing 100% short journeys as the soot and carbon build up will increase rapidly.

[Dave fitch]

I have exactly the same car (2.0 ultra) and the same thing happening but have driven a BMW diesel for four years doing exactly what I am doing now mileage and speed wise and only ever noticed about four regens in 40,000 miles this does a regen about every 250 miles and the fan has been running after switch off a number of times and WITHOUT THE REGEN SMELL.

I read on another forum that this is because there is a minimum amount of water used to cool the engine block so that the engine heats up faster to give improved economy.

Is that not correct then?

Are people saying that if you drive less than say 50 miles a day then an ultra is not suitable? this must discount a vast majority of the population from being able to drive an Ultra and with no petrol alternative surely makes the car uneconomical for Audi to build.

[wildbore]

I read on another forum that this is because there is a minimum amount of water used to cool the engine block so that the engine heats up faster to give improved economy.

Is that not correct then?

Yes, you are spot on.

Manufacturers are reducing the amount of water in the engine block to speed up warm-up time to increase economy. In fact, on some engines Audi now have a water pump that is mechanically disengaged completely during warm up to get the engine up to temperature even faster. Manufacturers are also making the engine blocks lighter to decrease the thermal mass and further aid a quick warm-up. As a result, engines are much less able to manage the sudden "dump" of heat when they are turned off - they rely on the fan to dissipate the heat that once would have been absorbed by the block and the water jacket.

It was -6 the other morning, I drove one and a half miles on slippery roads so I drove very gently with minimal throttle and without needing to stop at traffic lights or in a queue, and when I arrived and turned off the engine the fan came on. I have a petrol engine, so it certainly wasn't a regen!

[M1tchy]

My fan has come on a few times in the past few weeks, normal daily drive is quite short and at weekends it's a 15 mile high speed run to town. I normally get a good 300mile run to see family etc but not happened recently due to work hence the fan coming quite a lot.

I've just been for a 90 min drive to hopefully clear things up as it will still be a while until I can get a good run in her.

The wife will soon be living 4 hours away so should be OK after weekend commutes.


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[loz65]

Thanks again for all the feedback.

Thought I'd kill two birds with one stone, so took the mutt for a long walk on Formby beach, which involved about an hour's drive on the M6 each way, where I stayed above 2,000 rpm at around 70 mph for the journey up, so hoping this will have helped. Just two questions, having looked at what the manual says about the DPF:

It mentions about an indicator light coming on, stating that the DPF requires regeneration. Should this have therefore come on for me before the fan came on, or does this only come on when the car can't manage to do the regeneration itself and therefore requires the driver to do this?

In which case, from looking at the manual and I quote "Drive at a speed of at least 60 km/h (i.e. less than 40 m/h) for about 15 minutes with the selector in position S and keep the engine speed at about 2000 rpm." This is less than the 30/40 mins that others have said is required to do the regeneration - is the manual therefore being economical with the truth?!

It also says do this until the indicator light goes out once the process has been completed successfully. but in my case perhaps the regeneration with the fans had already done this, since I never saw a light?

Bit confused....

[Eshrules]

I believe the light would come on if you needed to complete an active DPF regeneration. In the main, passive regenerations should keep the DPF in good condition.

There's an interesting read about it here (http://www.fordownersclub.com/forums/topic/47310-focus-titanium-tdci-2012-engine-fan-running/?do=findComment&comment=288074) (ignore the bullish staff).

The specifics of and criteria to be met in order for a passive regen to begin will no doubt differ between car makes and models but the general idea is the same.

A spirited blast down the motorway for a decent length of time should ensure you maintain a healthy DPF.

I would however, recommend you consider a petrol car the next time you come to purchase unless your requirements/mileage change.