Having trouble finding any kind of info on that particular model -
AM78-HV4V...... From your original post, it sounds like this is just
a motor, with a pulley, driving a larger pulley via a belt, as you
mentioned giving the "fan" a spin. Anyway, ya gotta locate the motor,
and take the end bell off to gain access to a centrifugal switch
internal to the motor. The switch has a set of contact points on it
which close with the motor at rest, putting the cap into the circuit.
When the motor starts up, centrifugal force causes the switch to open
up and takes the cap out of the circuit until it's needed for the next
start. Arcing, pitting, dust, dirt, etc., can keep the contacts from
making contact with each other when the motor is at rest. I suggested
tapping on the end bell of the motor when trying to start it as
sometimes that will let the contacts actually touch each other and get
the cap in the circuit to start the motor. That will tell you if the
cap is good or not as well as letting you know that the contacts are
dirty. I can't see the motor so it's hard to tell you how to take it
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