I wonder if one of you electrical geniuses can help?
A while back I acquired a small portable compressor. It is a 240v, single phase, brushless, capacitor start machine. Marketed by SIP under the model name of Airmate WM39 it is probably between fifteen and twenty years old.
When switched on the motor 'hummed' but would not run. If helped with a flick it tried to turn but never more than about half a rev.
A new capacitor of the same spec. made no difference.
A peek inside the end cover showed no sign of burning or damage.
The cylinder, piston and con-rod were removed to lighten load. Like this it would run - with the help of a flick to get it going - for about twenty seconds; when it would slow and stop. The casing after these attempts was warm but not hot. No nasty smells were made!
A complete strip down revealed no physical damage whatever. All was clean, bright, and un-burnt. There were no marks on the rotor.
There are two pairs of wires from the stator; one pair to the switch and the other pair to the capacitor. None of these are down to earth. There is a satisfactory earth wire in place. Across the switch wires there is a 6 ohm resistance, and across the pair to the capacitor there is 10 ohms.
Please Teacher - what is wrong with my little machine?