ef falcons have a pair of 2 stage cooling fans can anyone tell me how and when they are switched to 2nd speed as my car seems to run up near top of "m" on temp gauge even though it never used to. 1 day i was idling with aircon on and temp was up to "m" so i decided to stop car and restart when i did fan was roaring which it wasn't before and temp went down quickly.I had a subaru sometime back and i had to replace the fan sensor as over time the engine temp had to be higher and higher as sensor must gain resitance or what ever and takes a higher temp to switch on cooling fan so i am wondering if same problem exists .I have had the car fro 87,000km to 270,000 km .

Yes, I can tell youi how they are wired up .. But its now 1:41am and I can't be f**k writing and essay on it now ... so yeah

but the quick run down is they both run of 12V, when the slower speed comes in they move from series to paraelle to drop the volltage into 6V to spin slower ..

Make snce?

On the EF they use a really stupid 4 relay setup to achieve what a 3 relay setup can do. It is as au2slow said, they're switched to running in series at low speed so 12v is distributed across two motors, each motor therefore receives approximately 6v each. At high speed the relays switch the fans to run in parallel so each motor gets the full 12v.

Fans on/off and low/high speed is controlled by the EEC via feedback primarily from the engine temp sensor, air con compressor input and auto trans fluid temp. I say disconnect the auto trans fluid temp sensor and let it die a painful death then put a manual in. Sorry for the sideways direction this post went

When the engine thermostat gets to 3.7kohm then the themofans kick in at low speed. I dont know when the high speed point is. The thermostat is a negative temperature coefficient type which means it reduces its resistance as it increases in temperature, therefore a hotter engine will have a lower resistance.

Thanks for your input now that i have it i will look into it further thanks again

Mine dont work at all :S anyway i can check them without going to a sparky cars done about 303,000klms

hot-wire them? .

I have the same scenario as Pookey. After a while of driving with aircon on and engine hot, my fans just don't go to its high speed. But if you stop and turn off the engine and start again, they go blowing like crazy again.

Yeah, I thought of hot-wiring one of the fans using the a/c compressor clutch activator signal to activate it (using a relay of course). But would this cause an error signal to the ECU? If yes, would it affect how the engine would run?
I don't have a clue really.


Cheers

Yep, my problem aswell ! (this is seeming contagous!)

well i got opposite problem, as soon as temp gauge hits the normal bracket (did know exact temp but cant remember (88.0??) the fans run on low speed....

My fans never seem to go on - what temperature are they meant to turn on - what letter on the temp gauge does everyone elses fan turn on. Mine is manual EF xr6 if that makes a different.