How to check if a capacitor is working without a multimeter?

Checking whether an HVAC capacitor is working without a digital multimeter relies on careful observation of motor behavior and physical inspection. First, listen closely to your outdoor condensing unit or indoor air handler when the thermostat calls for cooling or heating; if you hear a loud, rhythmic humming or buzzing sound from the motor compartment but the fan or compressor fails to spin, it strongly indicates a dead capacitor failing to provide starting torque. Second, inspect the capacitor physically for any obvious signs of damage, such as a bulging or domed top lid, cracked plastic casings, or oily fluid leaking from the terminals. Third, you can attempt a manual spin test on the fan blade with a stick; if the fan starts running after a manual push, the capacitor is dead. You can verify failure when visual deformation and humming are present.