So I've recently found out my cooling fan doesn't come on high speed when the coolant gets hot unless the aircon is on, so the fan works on both high and low speed when the aircon is working, is this likely to be the fan control module at fault?

Thanks in advance, Michael. 

If I remember correctly, it is designed to work as you describe.

 

Regards

The fan won't come on at all even if over heating unless the aircon is on. 

The low speed operation is controlled by the fan temp switch in the radiator, if you short pins 1 & 2 (red/yellow pin 1 & red/white pin 2) this should make the fan run on low speed, if you short pin 2 & pin 3 (red/black) this via the fan controller should make the fans run at high speed, when you select the A/C ON the fan controller forces the fans to run at high speed