How do you check a start capacitor?

Hello, I'm a professional electrician with a wealth of experience in electrical system maintenance and repair. When it comes to checking a start capacitor, it's crucial to ensure that you're taking the right steps to diagnose and potentially replace a faulty component. Here's a detailed guide on how to check a start capacitor:

Step 1: Safety First
Before you begin, always ensure to turn off the power to the motor you're working on. This is to prevent any accidental electrical shock or damage to the equipment. Use a voltage tester to confirm that the power is off.

Step 2: Removing the Start Capacitor
The start capacitor is typically located near the motor's terminals. It's a cylindrical component that can be easily identified by its shape and size. Carefully remove the capacitor from its mounting bracket or clips, ensuring not to damage any wires or terminals.

Step 3: Visual Inspection
Once removed, perform a visual inspection of the capacitor. Look for any signs of damage such as bulging or leaking fluid. A bulging top indicates that the capacitor has likely failed due to excessive heat or age. If you notice any fluid, this is a clear indication that the capacitor has ruptured and must be replaced.

Step 4: Using a Volt-Ohm Meter
To further diagnose the capacitor, use a volt-ohm meter (also known as a multimeter). Set the meter to the resistance (ohms) setting. If your meter has an auto-ranging feature, it will be helpful in this step.

Step 5: Testing the Capacitor
Touch the two terminals of the ohms meter test leads to the start capacitor's terminals. A good capacitor should show a low resistance reading that increases over time. If the reading doesn't change significantly or if it's very high from the start, the capacitor is likely faulty.

Step 6: Checking for Capacitance
To confirm that the capacitor is functional, check for capacitance. A capacitance meter or a multimeter with a capacitance function can be used for this purpose. The capacitance value should be close to the rated value printed on the capacitor. If it's significantly lower, the capacitor may not be providing the necessary start-up assistance to the motor.

Step 7: Replacing the Capacitor
If the tests indicate that the start capacitor is faulty, it's time to replace it. Ensure to choose a capacitor with the same capacitance and voltage rating as the original. Incorrect ratings can lead to further issues or even damage to the motor.

Step 8: Reinstallation
After replacing the capacitor, reinstall it in the motor, making sure to connect the wires correctly. Double-check all connections before turning the power back on.

Step 9: Testing the Motor
Once everything is reassembled, turn the power back on and test the motor. If the motor starts and runs smoothly, the replacement was successful.

Step 10: Documenting the Repair
Finally, it's a good practice to document the repair, including the date, the capacitor's specifications, and any other relevant details. This can be helpful for future maintenance or troubleshooting.

Remember, working with electrical components can be dangerous if not done correctly. Always follow safety guidelines and consult with a professional if you're unsure about any step in the process.

StepsRemove the start capacitor. ... Examine the capacitor for bulging or fluid. ... Use an analog or digital volt meter. ... Touch the two terminals with your ohms meter test leads. ... Check for capacitance, if the capacitor is alive.