When do each of the twin thermo fans turn on?

[XF_Pilot]

Hi guys,

I am interested in finding out how the twin thermo fans work in our AUs.

I know that when the air con is on that both fans run automatically.

Am I correct in saying that they are variable speed also?

What I would like to know is when does the first one activate? When does the second one activate also or is it only when air con is used?

Any info would be great!

[Maka]

80c then 110c iirc? You can put the dash in diag mode & check, if the a/c capillary tube is blocked low speed fan will come on earlier too apparently. Good luck!

cheer's, Maka

[auIILTD]

Hi XF.

I cannot confirm with a 6 cyl, but reading the stock V8 tune, it is based around an 198 DegF (92 DegC) Thermostat. Low fan speed kicks in at 210 DegF (98.9 DegC) and High fan kicks in at 224 DegF (107 DegC).

It would be fairly safe to assume the I6 is close or similar.

My understanding is that one fan kicks in at the low value and the second fan kicks in at the high value. I do not believe that they are variable speed - I have not seen any hardware or tune config to confirm they are variable.

Cheers
Stu

[JC]

Originally Posted by auIILTD

Hi XF.

I cannot confirm with a 6 cyl, but reading the stock V8 tune, it is based around an 198 DegF (92 DegC) Thermostat. Low fan speed kicks in at 210 DegF (98.9 DegC) and High fan kicks in at 224 DegF (107 DegC).

It would be fairly safe to assume the I6 is close or similar.

My understanding is that one fan kicks in at the low value and the second fan kicks in at the high value. I do not believe that they are variable speed - I have not seen any hardware or tune config to confirm they are variable.

Cheers
Stu

My understanding is somewhat different and is as follows:

With AC on, both fans run on low speed. This speed is achieved by running the fans in series, so the 12V is split between them, meaning 6V each, which only powers the fans to turn at roughly half their max.

When the temp sensor hits the figure required (as per Stu's figures above), both fans kick into high speed mode; this is achieved by switching the circuit to run the fans in parallel, meaning that each fan gets a full 12V resulting in the fan running at max speed.

I run AU fans in our explorer, and this was how I originally had them setup based on the research I did to find out how to make them low/high speed. if you ran one fan at high speed, the sound would be quite loud even just for one fan, but at low speed wired in series, they are barely audible - I have to put my hand behind them to feel that they are working.

The setup I now run with the AU fans in the explorer is the low speed fans run whenever the car is on (engine on), a supplementary 10" Davies craig fan fitted to the back of the AC condensor comes on when the AC is on (and then blows air onto the front of the radiator), and the AU fans come on high when the temp sensor hits around 82*.

[XF_Pilot]

Ok that's helpful guys. It is concerning a track car that will have no air con. I was just concerned that the second fan was only associated with air con. As long as it will come on at high temp then that's fine.

Thanks!

[JC]

Originally Posted by XF_Pilot

Ok that's helpful guys. It is concerning a track car that will have no air con. I was just concerned that the second fan was only associated with air con. As long as it will come on at high temp then that's fine.

Thanks!

High speed always comes on when the car hits preset temp, regardless of AC on or not.

Wiring diagram attached:

[XF_Pilot]

Great info. Thank you. Coming on in stages is great, when I have the J3 chip done I will get them to drop the switch on point for the high speed and leave the rest alone I think.

[Maka]

A bit more info (aufanboy post from au2 wagon overheating) -

http://fordforums.com.au/showthread....on+thermo+fans


Hey,

The sensor is connected to the ECU, which then sends the temperature info (along with other stuff) to the dash cluster via a serial data connection. So if your temp gauge is working then the sensor must be working. The fans should come on low speed when the gauge reaches the last mark before the N (of Normal). They should then switch into high speed mode (jet taking off) at about 105 degrees, which on an AUII will be just between N and O (the gauge is faked somewhat and sits in the same spot from 92 to 110ish). I would replace all three relays and start the car and check for low and high speed fan operation.

Here's the schematic from the manual:
http://www.fordwrm.co.za/manuals/For...on_auII664.pdf
and
http://www.fordwrm.co.za/manuals/For...on_auII665.pdf

cheer's, Maka

[NCII40]

Originally Posted by Maka

A bit more info (aufanboy post from au2 wagon overheating) -

http://fordforums.com.au/showthread....on+thermo+fans


Hey,

The sensor is connected to the ECU, which then sends the temperature info (along with other stuff) to the dash cluster via a serial data connection. So if your temp gauge is working then the sensor must be working. The fans should come on low speed when the gauge reaches the last mark before the N (of Normal). They should then switch into high speed mode (jet taking off) at about 105 degrees, which on an AUII will be just between N and O (the gauge is faked somewhat and sits in the same spot from 92 to 110ish). I would replace all three relays and start the car and check for low and high speed fan operation.

Here's the schematic from the manual:
http://www.fordwrm.co.za/manuals/For...on_auII664.pdf
and
http://www.fordwrm.co.za/manuals/For...on_auII665.pdf

cheer's, Maka

When in diagnostic mode on the cluster, Mine reads 92* between the N and O. How come the gauge is faked?

[Graeme77]

Can anyone tell me why my au series 2 one tonner overheats only when I put on the
air-con?
Driving without the air-con on no problems,not one drop of fluid losses,but when I turn the
air-con on I lose most of the coolant

[Maka]

Hi NCII4.0, not sure why the temp gauge is faked, have heard of au dash's giving false temp readings & boiling too unfortunately. Maybe the sensor is two stage not variable idk.

cheer's, Maka

[NCII40]

Originally Posted by Maka

Hi NCII4.0, not sure why the temp gauge is faked, have heard of au dash's giving false temp readings & boiling too unfortunately. Maybe the sensor is two stage not variable idk.

cheer's, Maka

Thanks for the reply Maka

I am looking at changing the sender over to make it variable
Hoping an E series sender will work

[mcfly94]

Mine sits at completely different spots for temps around 190f in comparison to the 210's gauge works perfectly fine in mine wouldn't say it's dummy gauge for looks