Running capacitor feeding inspection

Should you test a capacitor under load?

When you’re constantly checking capacitors as a matter of regular testing and maintenance, testing the capacitors under load (while running) is a great way to confirm the capacitor is doing its job under real load conditions, which is also more accurate than taking the reading with the unit off.

How do I know if I need a replacement capacitor?

Be careful not to touch the meter probes as you attempt to get a good, solid connection to the metal connection spades on the capacitor. If the measurement is more than 10%, we suggest a replacement. Taking a picture is one of the easiest ways to remember before removing the wires.

What is a run capacitor?

A capacitor stores and releases electrical energy during every cycle change. A run capacitor is specifically sized to create the ideal phase shift for optimal running efficiency and power usage by the motor. Contrary to what you will hear, a capacitor does not “boost” the voltage or create any extra energy.

How do you test a capacitor?

Test using a meter that is pre-tested to a known voltage source and check L1 to L2, L1 to ground, and L-2 ground to ensure no voltage is present. Before testing, touching, or removing the capacitor, you need to discharge it. Do this using a high-resistance resistor bridging HERM and Fan terminals across to C or across a single capacitor.

Can you use a screwdriver to discharge a capacitor?

For this reason, many techs opt to use a screwdriver to discharge, which is a controversial but common practice. (HERE is how we discharge capacitors.) To remove, disconnect the wires on the top of the capacitor and remove the strap holding the capacitor in place. Apples to apples: You must use the same MFD rating capacitor during this process.

What happens if a run capacitor fails?

If the run capacitor is failed, the motor often won't run in the case of high torque motors like a compressor, or in the case of fans, they may run backward or slowly or with high amperage or overheat. A run capacitor fails due to: Many will say a failed motor “takes out” the capacitor. In actuality, a failed or weak capacitor can take out a motor.