Audi A3, 2015, 2.0 TDI 184 - Cooling fan kicks in frequently, not overheating?

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Tue 11 Jul 2023 09:11
Audi A3, 2015, 2.0 TDI 184 - Cooling fan kicks in frequently, not overheating? - carnut1980

Hi all, my main fan kicks in quite often, no overheating.

Temp gauge reaches middle and stays there.

The other day, fan kicked in before gauge reached middle.

Could this be a faulty CTS?

79K miles, full history, recent timing belt and water pump.

No other issues. Drives perfectly

What should I check for?

Coolant is correct level and ratio

Cheers

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Tue 11 Jul 2023 09:22
Audi A3, 2015, 2.0 TDI 184 - Cooling fan kicks in frequently, not overheating? - craig-pd130

Could be related to DPF regeneration, the fan will always come on when a regeneration is happening to help disperse the underbonnet heat from the hot DPF.

At nearly 80K miles the DPF probably has a lot of ash in it which can't be cleared, so regens to try and clear soot build-up will be more frequent than they used to be.

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Tue 11 Jul 2023 09:27
Audi A3, 2015, 2.0 TDI 184 - Cooling fan kicks in frequently, not overheating? - carnut1980

OK. But i do plenty of motorway miles.

I also occasionally use DPF cleaner/fuel additive.

No smells, no lights on dash, no loss of power

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Tue 11 Jul 2023 09:22
Audi A3, 2015, 2.0 TDI 184 - Cooling fan kicks in frequently, not overheating? - craig-pd130

Could be related to DPF regeneration, the fan will always come on when a regeneration is happening to help disperse the underbonnet heat from the hot DPF.

At nearly 80K miles the DPF probably has a lot of ash in it which can't be cleared, so regens to try and clear soot build-up will be more frequent than they used to be.

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Tue 11 Jul 2023 09:28
Audi A3, 2015, 2.0 TDI 184 - Cooling fan kicks in frequently, not overheating? - elekie&a/c doctor
During dpf regeneration, engine temperature increases. The cooling fan will run more often to stop overheating. Engine cts also runs the engine temperature gauge . .

Edited by elekie&a/c doctor on 11/07/2023 at 09:29

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Wed 12 Jul 2023 11:16
Audi A3, 2015, 2.0 TDI 184 - Cooling fan kicks in frequently, not overheating? - mickyh7

The DPF turns soot into Ash. In doing so it reduces volume.

However, after many regenerations, the ash will ultimately fill the filter.

The filter is a Serviceable item.

As much as the car tries to burn off more soot, there is no where for it to go.

It will get stuck in regen mode, hence the fan, I'll also bet your using more fuel?

Everytime the regeneration fails, diesel, which is used to superheat your DPF, will get dumped into your sump, diluting your engine oil. This will be your second future problem.

New filter is my guess. Or try a clean out ( I don't think they work very well on colleagues experiences).

Most people when they see the price of a new filter, £1000+, choose to have the DPF mapped out!

Edited by mickyh7 on 12/07/2023 at 11:18

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Wed 12 Jul 2023 20:21
Audi A3, 2015, 2.0 TDI 184 - Cooling fan kicks in frequently, not overheating? - carnut1980

As stated, no other issues.

Excellent MPG, and power.

No lights on dash, no smoke or bad smell.

Had codes read anyway.

Turns out the secondary CTS is not working.

IE default temp reading was minus 40.

Is this sensor easy to locate and change?

Cheers

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Wed 12 Jul 2023 20:34
Audi A3, 2015, 2.0 TDI 184 - Cooling fan kicks in frequently, not overheating? - elekie&a/c doctor
Possibly the sensor in the lower radiator coupling or hose .
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Mon 17 Jul 2023 17:35
Audi A3, 2015, 2.0 TDI 184 - Cooling fan kicks in frequently, not overheating? - carnut1980

Hi. I did have the codes read. I was told the secondary CTS is no good/not showing a reading.

Hence the default reading was minus 40 (Celsius?)

I always assumed there was only one CTS?

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Mon 17 Jul 2023 18:18
Audi A3, 2015, 2.0 TDI 184 - Cooling fan kicks in frequently, not overheating? - elekie&a/c doctor
Not any more . Most cars these days have “smart “ cooling systems that can divert/ control the flow of coolant through the engine . This means that more ct sensors are needed to monitor the temperatures in various locations. Recently looked at an Audi A5 , think it had at least 4 sensors.
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