Technical How is the radiator fan controlled?

[NeilB]

On a 2000 (MK2) 1.2 ELX how is the radiator fan controlled? What makes it kick in? I see there is a resistor on the fan itself. What is this for? Is that just for the temperature gauge inside the car? What makes the relay trip when the temperature gets too high (and what temperature does the fan normally kick in on everyone elses car? 3/4?)

Thanks,
Neil

 

[Neo-The Matrix]

IIRC there is a temp sensor on the block, that sends the voltage signal to the ecu, the ecu trips a relay (found in the fuse box in the engine bay) which in turn switches on the fan.

 

[NeilB]

If I want to bypass this sensor to just make the fan kick in, how do I do this?

The resistor contacts are all green and corroded (like when a battery leaks). One end of the resistor has come unsoldered but is still touching where its meant to but its covered in this green stuff.

As you can tell, I'm not a mechanic

 

[NeilB]

Here are some pictures of under the bonnet

This is the radiator resistor which fell apart in my hands (see pic 2)

See how its all corroded? Is there a way I can short this out to test the fan?

This is how my water filler looks, the white on it, does that look as if its been overheating?

Is this fluid from my air con? Or heater matrix??

Thanks,
Neil

 

[NumanR]

Aircon

 

[T14086]

You can bridge out the relay but if your not comfortable with this then dont try it,you can blow the ecu! Buy a new resistor,fan cuts in about halfway on temp gauge.

 

[Neo-The Matrix]

Temp should be half way for fan to kick in.

I think you did have a minor overheat there.

The way I test the fan is to go at the fan motor itself, there should be 2 wires on the motor, disconnect them. Then wire the +ve side of the motor to battery + and the -ve side of the motor to battery -.

If you do not know what you are doing do not continue cause I do not want to be responsable for loss of limbs, bad ecus, messed up fan motors etc...

 

[faster4_tec]

Has your car been in the sea or something, as it is seriously corroded under there!!

 

[T14086]

LOL,poor guy wont sleep tonight now!

 

[NeilB]

Right we're making progress. Proven today it's the radiator fan thats broken. Bypassed the relay and supplied 12v direct to the fan and it's dead.