Fan operation and testing

[Cableguy]

Hi guys , in the bid to sort any niggles before a track day id like some info on when the fan kicks in and how its controlled please.

Where should the temp sit on the gauge ? bang on halfway or is it allowed to move around until the closer digits ? On my previous cars (mainly rovers) they sit dead middle and anything over is considered overheating.

At what point on the gauge should the fan come on ?

And last but not least, is there a way of testing the fan ? again previous cars unplugging the cts made the fan come on, do these use a sensor in the rad that i can just short out ?

Cheers :)

[Cableguy]

Ok , did some searching and got a few answers guys , so cheers.

It appears that the temp sensor in the rad controls fans whilst its running , and the CTS controls when its turned off ?

Third digit on the gauge before fan comes on , but whats the highest it should go ?

I hear a few mentions of anti perc ? what is this ? IVe heard a little pump running in the pipe down underneath the battery when i turn the car off, is this the "anti perc" whatever that is ?

Cheers

[cliokiz]

Ok , did some searching and got a few answers guys , so cheers.

It appears that the temp sensor in the rad controls fans whilst its running , and the CTS controls when its turned off ?

Third digit on the gauge before fan comes on , but whats the highest it should go ?

I hear a few mentions of anti perc ? what is this ? IVe heard a little pump running in the pipe down underneath the battery when i turn the car off, is this the "anti perc" whatever that is ?

Cheers

Ok to answer your questions...

Yes it's the temperature sensor on the radiator that triggers the fan when the ignition is on or when the engine is running.

You can test this circuit by just shorting the two pins in the plug and you'll hear the relay click and the fan will activate (mind your fingers...)

You can test the fan switch by plugging it in whilst the ignition is on and dropping it in some boiling water. Alternatively get the car up to temperature and the standard fan switch should activate the fan just after the third major mark on the dial (it's quite close to the top of the guage).

If the guage starts to reach the last few major marks on the dial then the car will start to overheat. Not good.

There is a sensor on the thermostat housing, not the CTS, but next to it (brown i think), which is another temperature sensor for the anti perculation system.

When the ignition is off, a reading will be taken from this and if it's over a certain temperature, the anti perculation system will be activated, the radiator fan will be on for around 9 minutes as well as the water pump you mentioned beneath the battery to circulate the coolant.

Hope that helps.

[cliokiz]

Oh also it's very common for the wiring to break to the radiator fan switch plug, check the wiring there and ensure it's intact otherwise the fan might not work at all.

[Cableguy]

Ok , had a butchers...

Anti purculation system is working fine , water pump runs after turn off when its hot , but the fan doesnt run at this stage and neither does it run when the engine gets hot.

Fan spins freely so ill run 12 volts up to it tonight and see if its knacked.

Any idea on wiring path and where relays are located so i can track any faults down ?

Cheers

[cliokiz]

Just give the fan a direct +12v feed. If it works, the issue is elsewhere, if it doesn't, then the fan is probably the issue.

Not too sure about the wiring but i know the relay for the fan is in the relay box behind the battery.