Espresso Tech 101: Testing a Motor Capacitor

The following instructions demonstrate the procedure for testing the capacitor associated with the electric motors in espresso machines and grinders.

Tools needed:
- Multimeter
- Insulated screwdriver


1. Make sure the machine is powered off and unplugged. Disconnect the power leads from the capacitor.
(These instructions show an uninstalled capacitor, it is okay to leave the capacitor in the machine after removing the power leads.)

2. Discharge the capacitor by bridging the blades with an insulated screwdriver.
(This method is only acceptable on low capacitance units.)

3. Identify the capacitor's capacitance rating in microfarads (μF) and take note of the tolerance level listed as a +/- percentage. This capacitor is rated at 60μF with a tolerance of ±5%, so we'll be looking for it to test between 57μF and 63μF.

4. Set your multimeter to the capacitance setting, marked with the "–|(–" symbol.

5. Touch the probes to the capacitor blades (AC capacitors are non-directional) and allow the multimeter reading to stabilize. This capacitor is testing within specifications.