How to do the 'spin fan by hand' test for capacitor ?

My air handler fan doesn't come on when it should. How do I test the capacitor, with the manual spin method? Do I just turn the heat on at the thermostat, then run downstairs and spin the fan and see if it starts up ?

I have already tried this, by the way, and the fan does not start up. Does that definitely mean it's not the capacitor?

 

The capacitor aids in starting but it can be good and the motor still be bad.
It can also be bad and spinning the motor by hand is not enough to get it started.

The cap is the least expensive part to change first.

 

Almost every electric motor need some kind of capacitor for starting. In electronic it is known effect as ELI-ICE, E = voltage, I = inductance and C = Capacitance, However without a beginning formal electronics education this discussion is beyond the limits this forum. Short version is the magnetic field of motor start needs a boost from the capacitor to spin up the motor in a timely manner. Regardless if the motor is not frozen it might eventually spin up without the boost. Most modern HVAC systems use a dual capacitor for the fan and compressor. Visual inspection of the capacitor could be useful, looking for bulging, leakage or corroded connections. With the power off the fan should spin easily with no sounds. Trying to spin a powered fan is dangerous and damaging, so I cannot recommend do such this at all

 

Welcome to the forums.

This is a small capacitor..... like 10mvd @ 370vac as it's in the air handler.... not the condenser.
These smaller light duty caps rarely bulge or give any outward appearance of being bad.

 

Have you verified that power is getting to the fan when it should be running?

 

Carbide, no I have not. Afraid to hook up any tester to it. What if I waived a 'voltage pen' near the wires? Would that detect power ?

 

Non-contact testers are not perfect, but should be good enough to verify the fan is getting power (or not). You should get a positive indication near at least one of the wires going to the fan as long as you check it when the fan should be running.