the motor is mounted sideways on top of the tank - the cover on the end of the motor is plastic and is round, as the motor is round. I emptied the tank and opened the valve on the bottom of the tank, so there is no pressure in the tank. I removed the cover on the motor and piston and attempted to start the compressor. It did momentarily start then stopped and began to hum like the piston or the motor was stuck. I unplugged the compressor and tried moving the fan and the piston and they moved freely. So I think there may be something wrong with the motor, but it is only a guess. Any thoughts?
OK I disconnected the hose from the tank before the check valve this morning and attempted to start the compressor. It started running for about 5 seconds then quit. So I am assumming it might be one of the capacitors attached to the top of the motor. One says "starting" and the other does not say what type it is.( I assume it is a running capacitor) How do I test either one of these capacitors?
OK, I bought a meter to test them from Lowes. I called the manufacturer to find out the proper way to use the meter. I just came in from testing the capacitors and the "start" capacitor registers 296 on the meter ( the capacitor shows it is rated for 250), so I assume it is more than sufficient. It does not give a + or - amount on it. I also tested the "running " capacitor and it showed 51. It is rated at 50 with a + or - of 5. So I assume this one is also sufficient. Any more suggestions?
Yes that is the rating on the capacitors. According to manufacturer, I was to leave only one of the leads off the capacitor as I was testing it. But I will try it again later with both off of each.
I retested with all the wires off and got a reading of 296.9 on the "start" capacitor and 51.5 on the "running "capacitor.
to your question about the running - when I did try that yesterday, it ran for the 5 seconds at a slow speed.
The cases of the capacitors are plastic so I didn't bother with that ohm test. My meter does not have that capability anyway.
I am surprised a meter without continuity, never seen one without it and measure voltage and capacitors.
Well, the only option at this point is to try a new START capacitor.Possibly it is breaking down on the surge while voltage is applied, even though the testing without voltage is good on the capacitance.I have seen caps fail when voltage is applied.The only reason I suggest a new cap, is it is not getting up to speed.The windings appear to be good since it does not trip a breaker at startup.If they were shorted then it would trip immediately.If it never reaches full rpm, the centrifugal switch cannot changeover to the run windings.It must start and reach full rpm , then the internal switch breaks the start windings in the motor and switches over to the run windings.It is not making it up to speed (if it runs slow for the 5 sec and stops), so there are only 2 things to stop it, bad winding or bad capacitor.Before I would call it a bad winding and motor replacement, I would want to get a $5-10 cap and try it to be certain.Now on another note, since you had transported it before the problem started I assume, I would check all connections inside the motor for tightness to be sure a wire did not slip off or cone loose anywhere inside the wiring compartment.