A good capacitor charges up to that voltage, so when you connect the meter to a good capacitor, you'll see the ohms start kind of low and go up really high as the capacitor charges up to the 1.5 volts or whatever your meter uses.
This can happen in a few seconds, or as fast as a half second.
A run capacitor from a Campbell Hausfeld air compressor is shown below.
I usually switch the probes back and forth a couple of times to make sure I'm getting that capacitance effect that sends the number negative and slowly rises back up. Only a capacitor does that. And it won't do it if the capacitor is shorted or an open circuit.
That will give you about a 95% certainty that the capacitor is good... again, the value of a capacitor rarely changes significantly enough to affect the running of a motor. Also, most motors have a start capacitor, which is only used to START the motor. The capacitor and the start windings are only used to get the motor up to speed. A few motors (usually the bigger ones) also have a run capacitor. While the method of checking the capacitors is the same, this whole discussion is about run capacitors because it's about a motor not having the power to keep running under higher loads...
To see if that's an issue, try to check your voltage at the compressor while it is running, especially when it is bogging down. If it is significantly below 110 or 220 volts, then you might get better power to your motor and see if it still does that.
Hope this helps someone!"
I am sure it will help lots of folks. Thank you very much anonymous contributor.