unless you are working as a maintenance engineer and can justify buying a milliohm meter
one option could be to connect a current limited supply and digital voltmeter to the motor connections
if the motor winding has a resistance of 0.1 ohm or less this could give you an inexpensive way to measure the resistance
Attachment 412452
with a 12 ohm 20W resistor and 12v supply connected to the motor terminals with the voltmeter
you can consider the current through the motor winding of 0.1 ohm (or less) as being a 1A constant current
so a voltmeter will see 0.1V across a 0.1 ohm resistor or 0.01V across a 0.01 ohm resistor
while its not as acurate as a £300 meter with 4 wire test leads with Kelvin clips
it will be close enough to check the 3 windings are the same
if the motor resistance is nearer to 0.5 ohm (or more) you will need to measure the current to calculate the resistance or increase the supply voltage to set the current to 1A
John