The fan (new or old) won't spin with just positive and ground connected - the signal wire controls the speed. You would need a function generator and know what sort of pulse width modulation BMW uses to manually operate it. It is better to plug the fan in and use software to force the fan on. A generic scanner won't do it, but there are several BMW specific software tools that will.

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David.X5
2001 X5 4.4i Sport
SOLD! at 160k miles