I have 2 or 3 of these in my shed (the single fans) - I was going to use them on a project car and got them for the right price.

The "module" is just a heat sensitive resistor. The hotter it gets, the more the fan gets driven, until the ECU determines that the second fan should be on.

And yes - 2 relay system.

Nigel

some had 1 fan others had 2 fans -

unit in fan shroud is a load resistor which is in series with the fan to give low speed when fan 1 relay turns on via ECU & associated sensors- with increase of temp ECU and associated sensors turn relay 3 on -
fan 2 relay (change over type) only used with 2 fan system-

bridge the fan resistor and fan should run on HI speed when relay 1 turns on if it does replace the resistor

some had 1 fan others had 2 fans -

unit in fan shroud is a load resistor which is in series with the fan to give low speed when fan 1 relay turns on via ECU & associated sensors- with increase of temp ECU and associated sensors turn relay 3 on -
fan 2 relay (change over type) only used with 2 fan system-

bridge the fan resistor and fan should run on HI speed when relay 1 turns on if it does replace the resistor