sounds like a lose connection........................................ ...........

Testing a capacitor use a Ohm meter after shorting out put leads across the terminals the Ohm meter will go up and slowly come back to 0 reverse and
do the same if good you will get the same result.
Are if you wont to invest about 20.00 Thea make a capacitor checker.

As already stated Thea can bit real good believe me i got hold of a large
one putting together a pale-phase