Cooling Fan

[vwroyd]

My cooling fan seems to come on without the gauge rising above 90`c, summer or winter it doesn't matter if it is stationary for a few minutes or more the fan will cut in.
Any information would be greatfully received.

Thanks :D :D

[Col]

If your aircon is on, it should be on all the time.

[vwroyd]

Thanks for that idea BigCol but this happens with the air-con on or off.

By the way it's a 2002 1.8T sport!!

Thanks again.

[Col]

Probably a faulty thermo switch then.

[rhencullen1989]

Hi, BigCol, where is the thermo switch located? a friend of mine has exactly the same symptoms. The radiator cooling fans seem to cut in, even on a very short journey. Temp gauge in the car reaches 90 and stays there. any other ideas. Ta, Rhencullen.

[GeorgeE]

What you need to bear in mind is that the fan control is a different sensor in a different part of the system to the temperature gauge.

So, the fan control is based upon the temparature of the water in the radiator, so if the radiator gets above a certain temperature the fan will cut in. This ensures the water leaving the radiator is cool enough to stop the engine temprature rising.

Now, the engine has its own thermostatic valve, this lets a mix of water that has just circulated around the engine (i.e. hot) and water from the radiator (cooled) back around the engine so that the temprature is maintained at a steady level, it is this level that is shown by the temparature gauge.

So in short, what you are seeing is the correct behaviour. The fan cuts in and out to keep the radiator water cool, the themostatic valve in the engine keeps the engine at a steady temperature.

[vwroyd]

Thank-you for that very comprehensive explanation GeorgeE, the car runs absalutely fine at all times so what you are saying sounds good.
Thanks again
vwroyd

[lucas88]

What you need to bear in mind is that the fan control is a different sensor in a different part of the system to the temperature gauge.

So, the fan control is based upon the temparature of the water in the radiator, so if the radiator gets above a certain temperature the fan will cut in. This ensures the water leaving the radiator is cool enough to stop the engine temprature rising.

Now, the engine has its own thermostatic valve, this lets a mix of water that has just circulated around the engine (i.e. hot) and water from the radiator (cooled) back around the engine so that the temprature is maintained at a steady level, it is this level that is shown by the temparature gauge.

So in short, what you are seeing is the correct behaviour. The fan cuts in and out to keep the radiator water cool, the themostatic valve in the engine keeps the engine at a steady temperature.


I've had a similar problem to this, (I say it's a problem but there have been no side-effects)
My cooling fan kicks in seemingly randomly, which makes sense with what you were saying. BUT, it allways comes on when I start the engine. It usually stays on for a couple of minutes then turns itself off.

Would I be right in thinking that this is most probably caused by a faulty radiator temp sensor? Or is this normal cooling fan behaviour?