One way to overcome this situation is by using "magnetically soft" material. Magnetically soft material has atoms that readily reverse polarity (a docile herd?) when exposed to alternating current. Naturally, since the reversing process happens more quickly, there is less wasted energy.
If you are confused by me saying that the current flows from positive to negative, that just happens to be a historical convention. People like Benjamin Franklin, who helped figure out the mystery of electricity back in the 18th century, believed it was a flow of positive charges, so it flowed from positive to negative. We call this idea conventional current and still use it to this day in things like Fleming Left-Hand Rule.
Do not coil excess cable of different types (i.e. motor power and feedback) together. An efficient transformer is formed at HF. Cable lengths should ideally be trimmed to fit the application. If excess cable cannot be trimmed, it should be laid in an ‘S’ or figure eight pattern.
Using the ohmmeter, find the pair of wires that has the highest resistence as measured in ohms. This will give you your common and lowest speed tap. Using each of these two leads in turn, find the pair that gives you the the second-highest resistance. This should provide you the common and second-lowest speed tap and should also allow you to isolate which of the two leads from the first test is the common.