Hi everyone,

I recently bought an AU XR8 220 manual. The previous owner replaced the radiator and put a set of FG thermo fans in it.

The car runs cool and has no problems there but the fans are always on!

They even run when the car is started from stone cold.

What I would like to know is what triggers the fans to run in the AU? This way I can hopefully find what is telling them to run all the time. Hopefully the computer is not involved.

Thanks, Jason.

The 6cyl has two sensors in the AC line... Small one does pressure and big one does temp... If the big one is disconnected I'm sure they run flat out all the time...

If you temp gauge shows normal then it shouldn't be that doing it, nearly has to be AC related... Same sensor that drives the gauge runs the fans via the PCM...

Cheers,
Tim

its the ecu that triggers when the fans come on low and high speed..

on the v8 the temp sensor on the heater pipe on the manifold is for both ecu and gauge.
if the one on the a/c is disconnected the fans will only run full speed when a/c is on..

I would go over the wiring to the fans and see whats been done, my thoughts are why put fg fans in the au when the au fans are perfect for the job.

also, being manual, has the car ever been converted from auto to manual?
if its still got the auto ecu the fans will run constantly, or if the ecu had ever been changed and had a auto ecu the same thing will happen..

i do believe the car has been converted to a manual from auto but it has also been tuned by bluepower, i would have thought they would have corrected that.

Why would it cause the fans to run all the time if it has an auto computer? any way of telling if its an auto computer?

I ran the fault codes through the sct tuner and got

P0480 - fan 1 control circuit and
P0481 - fan 2 control cciruit

Can anyone shed any light on what these mean?

if it still has the auto eco or auto tune file the ecu looks for a temp signal from the auto box and if it doesn't see the signal it by default turns fans on as it thinks the box is overheating...
but if your getting fan fault codes im thinking your fans are not connected to the factory wiring anymore and have possibly been wired to direct ignition power..
and because the ecu isn't seeing load on the circuit it is putting a fail code?

FG Fans specifically are a single unit arent they? - theyre driven differently off the relays, and the low speed is actually variable depending on heat load (via a resistive load in the shroud). The should work fine, but you'll need to wire them correctly, otherwise the ECU will detect the relays not causing the appropriate voltage drop, and turn them on.

If you have AC on as well, the speed of the Interior Fan can affect how fast the fans go when the AC is on.

I have found some wiring that has been looped under the dash. There was a switch on the fuse panel that was disconnected. This wiring has been looped behind it and runs under the fuse box in the engine bay. Looks as though they were controlling the fans manually? I will disconnect the loop and see if the fans switch off. I will also check the relays as you suggested