Engine fan doesn't turn off.

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Ah2
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Engine fan doesn't turn off.

Post by Ah2 » Thu Jan 16, 2020 10:24 am

Hi guys,
I have polo 6r and yesterday I realised my fan is staying on and running down my battery. Any advice on what could be the cause of this?? Im Completely lost!

RUM4MO
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Re: Engine fan doesn't turn off.

Post by RUM4MO » Thu Jan 16, 2020 2:20 pm

I'd think that it is one of three things:- fan control module faulty, ie stuck/welded contact(s), temperature switch that controls the fan(s) faulty, a wiring problem in between the two.

Edit:- to prove that it is not the temperature switch's fault, unplug the connector mounted on it. To check that it is not the wiring to the fan control module, unplug its control plug, ie the small one.

Ah2
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Re: Engine fan doesn't turn off.

Post by Ah2 » Fri Jan 17, 2020 5:52 pm

Thanks buddy... Where is the temperature switch located if you don't mind me asking?

RUM4MO
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Re: Engine fan doesn't turn off.

Post by RUM4MO » Fri Jan 17, 2020 10:38 pm

I've not looked for that on this mk of Polo, but typically it is on the radiator or a pipe close to the radiator.

Edit:- maybe tell us the engine and trans fitted to your car as I have a Haynes Polo 6R repair manual.

RUM4MO
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Re: Engine fan doesn't turn off.

Post by RUM4MO » Sat Jan 18, 2020 10:34 am

Haynes says "left hand side of radiator" - which means passenger side for RHD cars, for the location of the thermostatic fan switch - remember in some cars this switch will have 2 settings, obviously OFF when coolant is cold enough, ON-1 when coolant is over 90C and ON-2 when coolant is over 110C.
These are rough temperature figures, but on some Polos the fan will be 2 speed, so the slow speed gets switched on first to control/reduce the coolant temperature, if that is not enough fan cooling the temperature rises and the second switch position changes the fan speed to fast speed.
What can also happen is, the series dropper resistor burns out and so goes open circuit, so you end up with no slow speed only slight over heating then fast speed running of the fan.
You can tell if the fan is 2 speed by the number of wires going to the motor assembly, originally in most VW Group cars there were 2 cooling fans, both only ran at fast speed, but someone seemed to have a cunning plan to save a bit of cash and drop this down to 1 fan with 2 speeds.

Ah2
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Re: Engine fan doesn't turn off.

Post by Ah2 » Sat Jan 18, 2020 10:46 am

Hey guys, thanks so much for the advice. It's a polo MK5 engine size 1.2 manual.

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