My teacher told us a quick way to troubleshoot a compressor is to to use your ohm meter across the leads. He said start winding will read higher ohms than the run winding.
are you saying my ohm meter won’t actually read total resistance? Then what exactly is my ohm meter reading and is there an instrument that will read total resistance including impedance?
What a simple ohm meter does, is it applies a sample DC voltage across its leads, and measures the corresponding current that flows through the component it measures. The ratio between the two, is the read-out in Ohms that it gives you. It will also tell you whether you have continuity (finite ohms) or discontinuity (infinite ohms). You can only extrapolate this reading to the behavior in a circuit, when it is a pure resistive component you are measuring, and it is a component where you can expect a linear relationship between current and voltage. In other words, an ohmic resistance.
Ohm's law is not V=I*R as you have been told all your life. That is an algebraic re-writing of the definition of resistance. Ohm's law is that resistance is a constant for components and materials that obey it. It doesn't universally apply to every passive component, because other factors come in to play.
Inductance and capacitance, which are properties that are involved in a motor's circuit elements, can translate to a corresponding reactance in Ohms at a given frequency. This combines in a Pythagorean theorem formula with resistance in Ohms to get total impedance. Reactance refers to storing energy in a component, and releasing it at another part of the cycle. Resistance refers to dissipating energy in a component to another form of energy. Reactance depends on frequency in the opposite manner for inductors as it is for capacitors, while resistance of resistors is independent of electrical operating conditions.
An ideal inductance or electromagnet winding like you'd see in a motor, will measure zero ohms with an ohm-meter. The ohms you really measure are the parasitic resistance, that you get in a real inductor.
An ideal capacitor will measure infinite resistance with an ohm-meter, once the capacitor fully charges in the steady state, since there is no continuity across the gap between the plates. It will initially measure finite resistance that starts out at zero and grows to infinity with time, because there will be current in the circuit as a capacitor charges. You get initial continuity with a capacitor that eventually settles to a lack of continuity.
