Control = Violet perhaps ?

Control could connect to battery positive or to ground to turn fan on…

It could expect a PWM signal, or even an analogue variable voltage if variable speed control is expected.

Maybe check the wiring diagram of the donor vehicle for clues….

Possibly a two speed fan.

One wire will be common, the others may connect to different field windings (Although likely to be a PM motor) to provide the low and high speeds.

Akin to the rear wiper motors that were used on some cars.

Howard

As far as I can tell: Red +ve,Black -ve & Violet is control voltage so will probably be PWM signal for variable speed or less likely variable dc again to change speed,I would think these are specificly designed to be controlled by the heating & ventilation ECU,incorrectly connecting this will allmost certainly destroy internal control electronics so tread carefully & make sure of connections before you try them.

The diagram at the end of Michael's link shows the simplest option is to run the fan at full speed by connecting black to negative and both red and violet to positive.

Dave

You are overthinking this. If the maximum input voltage is 10V then feed the control wire from a potential divider with a 2.2 K resistor to +12V and 10 K to ground. This will give just under 10V on the control wire. Or use a 10 K potentiometer with one end grounded and the other connected to +12 V through a 2.2 K resistor, the slider on the violet wire for speed control. You won't need things like voltage stabilsers etc.

Excellent!