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Cooling fans don't work when the ignition's switched off


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#1 Rgm36

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Posted 30 April 2021 - 08:15 AM

So, on to the next issue. I've noticed that when I switch the engine off, the fans never continue to run.

 

I'm going to check this on the way home by getting it up to normal temperature on the motorway and then pulling into a layby and switching it off, rather than doing the A and B roads I would normally do on the way home before switching off.

 

I've tried searching but couldn't find anything, are there any connections or modules worth checking out? Has anyone come across this?

 

Many thanks


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#2 leemcalbanicoll

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Posted 30 April 2021 - 09:15 AM

Are they supposed too would have thought it would be pointless to fan the radiator with the coolent not pumping around, and would be a real drain on battery

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#3 northpole

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Posted 30 April 2021 - 10:36 AM

They only do it when the temperature under the bonnet is well above operating temperature( above 90 degrees Celsius)
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#4 Rgm36

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Posted 30 April 2021 - 06:18 PM

Are they supposed too would have thought it would be poi

 

They only do it when the temperature under the bonnet is well above operating temperature( above 90 degrees Celsius)

Ok, is there anyway to check the circuit? The temperature never seems to rise above 90º, so maybe that's it and there's no problem....happy to tick this one off and revisit if ever it does and they don't come on I guess.

ntless to fan the radiator with the coolent not pumping around, and would be a real drain on battery

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I remember that when I'd finished a motorway journey they would come on for a bit, but they don't seem to be doing that right now....


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#5 Rgm36

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Posted 30 April 2021 - 06:20 PM

Are they supposed too would have thought it would be pointless to fan the radiator with the coolent not pumping around, and would be a real drain on battery

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They always used to come on years ago when I'd just finished a motorway journey.....

 

 

They only do it when the temperature under the bonnet is well above operating temperature( above 90 degrees Celsius)

Cool, thanks. Happy to tick this one off then, plenty more to do! Is there a way to double check this circuit do you know? Wondered if there is an output check in Vagcom I could do?


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#6 northpole

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Posted 30 April 2021 - 09:22 PM

Just replace the thermostat as what you described is a clear Indication of a stuck thermostat

#7 adam-

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Posted 01 May 2021 - 08:19 AM

Slow or fast stage?  Check VCDS for coolant temp.  If it's managing around 90, they won't come on.  If AC is on, slow speed will work during ignition.  Fast only comes on when coolant >110 iirc.


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#8 Rgm36

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Posted 01 May 2021 - 09:38 AM

Just replace the thermostat as what you described is a clear Indication of a stuck thermostat

Thanks Northpole, I propably should in any case as it's been sat around for a couple of years....what is it about my description that points to a stuck thermostat?

 

Slow or fast stage?  Check VCDS for coolant temp.  If it's managing around 90, they won't come on.  If AC is on, slow speed will work during ignition.  Fast only comes on when coolant >110 iirc.

I'm not too sure on the stage of the fan, I need to check that. I would say it's coming on slow at the moment. Will VCDS show a different temp from the temp gauge on the instrument cluster then?


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#9 northpole

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Posted 01 May 2021 - 10:10 AM

The fact that you said it doesn't really hit 90 on the temp gauge... that's why I said just change it.

#10 Rgm36

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Posted 02 May 2021 - 12:17 AM

The fact that you said it doesn't really hit 90 on the temp gauge... that's why I said just change it.

Ah, no, sorry if I wasn't clear - it hits 90º and then stays there without moving until being turned off and cooling. This afternoon on my drive to work it stayed at around 70º for the 15 minutes I did A & B roads at 30-40mph and then as soon as I hit the dual carriageway and sped up it rose to 90º where it stayed for the next 35 minutes...on the way home I checked the gauge against the coolant temperature reading on VCDS and the gauge gets to 90º more quickly than VCDS where the temp was 75-80º for quite a while.....then as soon as I hit the motorway both got to the 90º mark and stayed there.


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#11 northpole

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Posted 02 May 2021 - 09:44 AM

in that case don't worry about the thermostat... just run a vcds check if you got no DTC's and the both the coolant temperature and the outside temperature show up oke than you have nothing to worry about.  



#12 Rgm36

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Posted 02 May 2021 - 03:50 PM

in that case don't worry about the thermostat... just run a vcds check if you got no DTC's and the both the coolant temperature and the outside temperature show up oke than you have nothing to worry about.  

Ok, will do, many thanks


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#13 adam-

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Posted 03 May 2021 - 03:08 PM

Ah, no, sorry if I wasn't clear - it hits 90º and then stays there without moving until being turned off and cooling. This afternoon on my drive to work it stayed at around 70º for the 15 minutes I did A & B roads at 30-40mph and then as soon as I hit the dual carriageway and sped up it rose to 90º where it stayed for the next 35 minutes...on the way home I checked the gauge against the coolant temperature reading on VCDS and the gauge gets to 90º more quickly than VCDS where the temp was 75-80º for quite a while.....then as soon as I hit the motorway both got to the 90º mark and stayed there.

 

The gauges inaccurately display temp to not worry the driver.  If coolant stays at 90 all the time, leave it alone.


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#14 Rgm36

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Posted 04 May 2021 - 01:31 PM

The gauges inaccurately display temp to not worry the driver.  If coolant stays at 90 all the time, leave it alone.

 

Great, will do, many thanks, one less thing to worry about!!


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