Category Archives: Air Conditioner Capacitors

Common Air Conditioner Capacitor Failure Symptoms

Capacitor Failure Symptoms

are sometime harder to identify without the right tools and expertise. the most common symptom of a bad capacitor is that the motors do not run. This is especially true for the compressor. Fan motors can sometimes run even with a bad capacitor but hidden damage is still happening to the fan motor. Fan motors can also run intermittently with a weak or bad capacitor. There are not always visible signs that a capacitor is bad. But there are times when you will see either a balloon shape on the capacitor or a split and leak. But this is not always visible when a capacitor is bad. It’s best to have an expert check the capacitor. There is a high risk of severe electric shock if a capacitor mishandled. This is not a DIY repair.

Types of Capacitors

Capacitors can be found in several different sizes and shapes. There may be one or multiple capacitors included in your ac with regards to the design. While the most popular capacitors are the types found on circuit boards, the ones most associated with air conditioning will be the bigger capacitors that assist start and run your motors. There are several motors present in an conditioner and heater systems:

  1. Compressor Motor Run Capacitor: Here is the most popular capacitor that fails. Most of the time these are duel capacitors, which means that there are 2 capacitors built into one. A duel capacitor will have three terminals on the top where a single capacitor will simply have two terminals on top.
  2. Outside Fan Motor Run Capacitor: That is the smaller capacitor found with or part of the Compressor Motor Capacitor. It helps start and run the outside fan that blows air through the outside coils.
  3. Indoor Blower Motor Run Capacitor: Similar to the outdoor fan motor capacitor, it is a small, single (two terminals) capacitor that will help start and run the indoor blower motor.
  4. Start Capacitor: Some models include an auxiliary start capacitor that helps jump start the motors. Most are found on the compressor. These are less common.

Why do capacitors go bad

When capacitors go south, they either go out entirely or they decline in strength. The decline is measured in the “capacitance” units called micro farads. When the capacitors are produced, they are labeled with their specifications capacitance and a range +/- from the design capacitance. This range is the allowable operating range, usually labeled in a percentage range, for the capacitor. If the capacitor starts to fail, the capacitance measured will be outside of the labeled range. Sometimes these are difficult to find any symptoms unless you have the proper tools. Warning, there is a risk of severe shock, so do not try this at home.

Diagnosing a bad capacitor

If a capacitor goes out completely, or is severely out of its operating range, it may prevent the motor affiliated with it from running completely. If the compressor motor is not working, then the air conditioner will not cool. If the outside fan is not working the compressor may cause problems and will short cycle or cease working. If the indoor fan stops, you’ll find that there is no air blowing through the vents.

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Why do HVAC Capacitors Need Replacing

Capacitors are very similar to batteries. They get charged up, hold this charge, then release it. The only difference between a capacitor and a battery is the amount of time it takes to charge and discharge. Batteries are slow to charge and slow to  discharge. Capacitors charge and discharge nearly instantaneous.capacitors

Several other properties are similar too. For example, they wear out over time, they have a shelf life, they lose their power capacity when exposed to extreme heat, and they can fail internally and leak. The one thing that makes them different also makes them dangerous. Since they can discharge in an instant, this means the current and voltage they hold can severely injure or even kill someone who does not know how to handle them.

The quality of a capacitor is dependent on the materials used to manufacture the capacitor. Some materials are better than others. There are capacitors that have 5 year warranties and cost more due to the materials. There are others that are made from cheap less suitable materials and the capacitors can fail within months.

HVAC technicians have a wide variety of choices from their distributors and sometime just go for the cheap brand so they can make lots of profit. Not to mention they get more frequent return visits. Most consumers are not educated on the brands or what to ask their technician. Check with your technician if he/she offers any kind of part warranty for your piece of mind.


Top 4 HVAC Repair Myths

  1. A technician said my coil is rusty therefore I must have a leak. Although likely to be true, it is not 100% accurate. The coil rusts when too much water or ice builds up on the coil over time. Ice can build up on the coil for other reasons, not just for leaks. Air flow has just as much impact on creating a frozen coil situation. Crushed ducts, poor design or dirty air York Air Conditionerfilters can all prevent enough warm air from flowing across the coil to prevent it from freezing. Proper maintenance and routine filter changes can help prevent frozen coils.
  2. My Capacitor is not swollen so it must be good. Not necessarily. A capacitor can be weak but not dead. A weak capacitor can wreak more havoc than a dead capacitor. Usually a dead capacitor will prevent the motor from running. Whereas a weak capacitor will allow the motor to run under poor conditions and quickly shorten the life of the motor. Motor replacements are expensive.
  3. A technician said a UV light would prevent dirt in my ducts. While a UV light helps prevent bacteria from growing on your coil, it does not prevent or destroy dust particles. Those pass the light unaffected and build up on motors and insulation that allows mold growth.
  4. I don’t need to maintain my heating or air conditioning system until it stops working. Although this is the choice most homeowners make, it is incorrect to assume the system will run fine without maintenance. Hidden dangers build up every year that a system goes without maintenance. Capacitors start to go weak (see item #2), compressors start to run hotter, drain lies build up with mildew. Delaying the maintenance will likely force the homeowner to spend more money on major repairs sooner than would be normal for a well maintained system. Maintenance does not guaranty your system will not need any repairs, but it does improve the life span of one of the most expensive systems in your home. You change the oil in your car every 3000 miles, why wouldn’t you have your system cleaned and inspected every year too.



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Air Conditioner Capacitors


Have you had an air conditioning company replace a capacitor recently? Have you ever wondered ‘how can I tell if the air conditioning capacitor really needed to be replaced?’ This video will show you one way to visibly tell if an ac capacitor has failed. This is not always the case, but if you do see your capacitor looking like this then it definitely has failed. Alexander Heating and Air Conditioning knows air conditioning troubleshooting and replacing a capacitor is always a common question from the homeowner. Warning: hvac capacitors hold an electric charge equal to the high voltage connected to it and can be a severe shock hazard. Do not touch the capacitor. So next time you are wondering what are some of the bad ac capacitor symptoms, you now have one of the most common symptoms to check.

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