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How to Test and Repair an Air Conditioner (A/C) Capacitor

How to Test and Repair an Air Conditioner (A/C) Capacitor
Most capacitors are found on circuit boards, and are quite small in size. However, those in air conditioners are large in size; they power the motors in the unit and are vital to the functioning of the machine. This article shows you how to check an A/C capacitor, and the proper procedure to repair the unit in a safe and efficient manner.
HomeQuicks Staff
Quick Tip
Summer is the time when most breakdowns occur in air conditioning units. This happens because this is the period during which the unit is most used, causing electrical overloads, overheating, and wear and tear of parts. Hence, it is advisable to buy and store spare parts at this time, to get quick and effective troubleshooting processes done, and bring your air conditioning back on track.

Keeping regular tabs on the maintenance of your A/C unit is the best way to prevent the chances of a breakdown. Cleaning and looking after the parts, such as filters, fans, and coils, will help in keeping the temperature of the unit in check, and keep the unit from overheating.
However, if your unit fails, don't panic. Before you make a call to the service technician to fix the problem, check to see if an old or faulty capacitor is to blame. If this is indeed the case, you can fix this problem yourself, which will save you valuable money and time. Also, replacing the capacitor requires no special tools. Anyone with a little DIY experience can successfully complete this job with ease.
What Causes an A/C Capacitor to Fail
There are four primary causes for the malfunction or failure of a capacitor:
  • Overheating: The capacitor of an air conditioner consists of components which are kept moist with lubricants and oils. When it turns hot, the components start to dry up, eventually ending up in a short circuit. This happens especially when the unit regularly crosses 70 degrees Celsius.
  • Old Capacitor: Even a well-maintained capacitor will eventually stop working due to wear and tear that occurs every time the A/C is turned on. Normally, it is expected to last for around 5 - 7 years, depending on the usage and external factors such as climate.
  • Damaged Parts of the A/C: Damage or wear and tear of the parts of the A/C, such as the fan or motor, will stop the capacitor from working efficiently, and eventually burst due to overheating.
  • Electricity Overload: This problem primarily occurs when the capacitor malfunctions and is continuously forced to provide power to the motors and compressor of the machine. Heavy fluctuation in voltage can also cause this problem to occur, eventually leading to the destruction of the capacitor.

Signs of Failure
If you suspect that the capacitor is to blame for your malfunctioning A/C, you need to make sure of the fact before you start the repair or call a technician. Check for the following signs to find out for certain whether the capacitor is faulty:
  • Visible wear and tear on the capacitor.
  • Chemical fluids leaking out of the unit.
  • Puffing up of the capacitor, which might lead to cracks.
  • Smoke or a burning smell emanating from the capacitor.

Air Conditioner Capacitor Testing
The easiest way to check if the capacitor is blown is to use a voltmeter. Another way is to check for a buzzing sound near the unit, and checking if the fan is working. If the fan isn't working despite the buzzing sound, there is a very good chance that the capacitor is not working.

Discharging the Capacitor
From the safety aspect, this is the most important step in the process. Extreme care has to be taken throughout this duration to avoid the risk of electrocution. This is because the function of a capacitor is to store electricity. So, even though you may have turned off the main power supply to the unit, it will still have enough power to shock you. To make the capacitor safe for handling, discharging it is extremely important.
  1. First, turn off the circuit breaker to the main unit, and use a tester to ensure that the power supply has actually stopped.
  2. Next, unscrew the side panel from the A/C unit and keep it aside to reveal the main assembly.
  3. To locate the capacitors, utilize the user manual. However, make sure that you do not touch any of the exposed wiring to avoid getting shocked.
  4. When you find the capacitors, holding only the insulated part of a screwdriver, place the metal end on the two terminals of the capacitor. Simultaneously touching both terminals will create a short circuit in the capacitor, and cause it to discharge.
  5. Repeat the process for all other capacitors that are nearby.
  6. Remove the screwdriver, and you can now start with the process of replacing the capacitor.

How to Replace an A/C Capacitor
  1. The capacitor is usually attached to the A/C unit by a metal band. Unscrew the metal band to release the capacitor.
  2. Next, make a detailed drawing which shows which wire connects to which terminal of the capacitor.
  3. Use a pair of insulated pliers to remove the wires from the capacitor. Be gentle with the wiring during this step to avoid touching other terminals in the assembly.
  4. Now that you have removed the capacitor from the A/C, fix the replacement to the unit in the same way as the original with the help of the diagram that you have made.

Tips to Buy a Good Capacitor
While shopping for a capacitor for your A/C unit, the size and shape of the component is not very important, and neither is the brand. The factor that one should focus on is the voltage and the micro farad μF reading mentioned on the capacitor. Although the voltage of a capacitor can be equal to or more than that of the original, the micro farad rating has to be exactly the same. In case the voltage and micro farad rating is not mentioned on the original capacitor, note down the model and make of the A/C, and show it to the salesman; this will help you get the correct components. It is always a good choice to buy more than one replacement. In case of another breakdown, it will enable you to carry out a speedy repair.

With these tips, it should be easy for you to repair an A/C capacitor, and get the unit up and running in no time. However, if you are not to confident with doing this yourself, find a good contractor. After all, the air conditioner is a very important system to keep your home comfortable and cool.
Disclaimer: This HomeQuicks article is for informative purposes only. If you are not well-versed with an A/C system, do not attempt this repair by yourself. Call in a reputed technician for the same.