I agree, I kept my old unit running replacing wires and capacitors &
even fans and blowers for 10 years before replacing the whole thing.
I've found that unless you can find an open connection it is likely a
capacitor & often a bad capacitor will fry a wire which will also need
to be replaced. Caps are a good first try, and much cheaper than a
house call. The main thing is that after you run through it with the
multimeter, turn off the power before poking around and still you
should treat it like it is hot.