Motor leads

For the fan on the left 12 v = 20i x R

Resistance (winding) = 12V/20i

Therefore your resistance for the motor winding will be around 0.6 ohms between the two leads to power the motor windings (positive and negative)

There's no impedance or reactance power factor other than unity 1 to worry about for dc circuits
 
For the fan on the left 12 v = 20i x R

Resistance (winding) = 12V/20i

Therefore your resistance for the motor winding will be around 0.6 ohms between the two leads to power the motor windings (positive and negative)

There's no impedance or reactance power factor other than unity 1 to worry about for dc circuits
Unless there is solid state components integral to the fan as in the picture you can't use ohms as mentioned
 
these are brushless dc motors, metering the leads wont give you anything useful. black+red, and black+yel as OP guessed. Yellow is DC+ if no red present. If red is present its DC+ and yellow is the tach output.
 
I tried to google up a data sheet for that fan for fun. Nothing to be found that I can see. The OEM must be in a basement in China.
 
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