Good advice.
Black would be negative and black/white is positive.
There are only two wires to the blower motor, and you can't do any damage with the above tests.
The reason for testing the positive circuit and the negative circuit seperatly is that they have different functions.
The negative circuit has the fan speed control stuff, aka the famous resistor pack and the fan speed switch.
The positive circuit is where all the fuses and relays are assocoated with.
Testing each wire will isolate what we are dealing with.
