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  • Writer's pictureRob Mitchell

Central Air Conditioner Problems

According to the most recent Residential Energy Consumption Survey, 88% of U.S. households use air conditioning. If you are in this group, it is a good idea to give your air conditioner a test-run early in the spring to check for any system problems. Turn it on for an hour or so on a day when you otherwise wouldn’t need it. Many people encounter problems testing their air conditioners, particularly after a dormant period.

Air Conditioner Problems

There could be dozens of reasons why your air conditioner isn’t working properly. How do you know which one is affecting you?


Following are some common central air conditioner problems you might encounter.


1. The air conditioner won’t turn on

A lack of power could be something as simple as a blown fuse or a tripped circuit breaker.  Check for these issues first. It could also be the result of broken or loose wiring or a thermostat problem.


2. Thermostat Problems

Your thermostat instructs your air conditioner when to start and how long to run. If its settings are not correct, your air conditioner may not work properly. Check the following if you believe you have a thermostat issue.


Replace the batteries if the screen is blank (programmable models)

Make sure your thermostat has power (smart models)

Check that the thermostat is currently set on cooling mode

Ensure your desired temperature setting is lower than the current room temperature


The older dial-type thermostats are subject to calibration problems. The newer programmable thermostats are not easy to program. If you feel you are having thermostat issues with a newer thermostat you many want to consult its manual to make sure you have properly programmed it.


3. Weak Airflow

Clogged or dirty filters can lead to numerous issues because the system has to work harder to pull air into the system. They can also make your air conditioner stop working if the coil freezes up. A disposable furnace filter should be replaced at least every three months. It may need to be replaced more frequently, depending upon the filter itself, how much your system is running and if you have furry pets in the home. A failing blower motor, leaking ducts, blocked vents or returns can all result in a weak airflow.


4. Frozen evaporator coil

An evaporator coil is the part of an air conditioner that absorbs the heat from the air in your house. It is located inside the air handler or attached to the furnace. Essentially, anything that reduces airflow to the evaporator coil can cause it to become frozen.  A dirty air filter, blocked vents and returns, or a failing blower motor can all cause insufficient airflow in the system. Over time, your evaporator coil may also become covered in dust, dirt, and pet hair. This will prevent it from getting the airflow it needs. Low refrigerant levels can also result in freezing of the evaporator coil.


5. Frozen condenser

An air conditioner’s condenser is the outdoor component of your air conditioning system. It is responsible for the condensation process that releases the heat collected from inside the house. It contains a compressor, fan and a coil. It can freeze up for the same reasons the evaporator coil freezes. Weak airflow, a dirty condenser coil, or low refrigerant. It may also freeze due to a dirty evaporator coil.


6. Refrigerant Leak

Your air conditioning system uses refrigerant to transfer heat from inside to outside. This refrigerant runs though copper pipes from the condenser to the evaporator and back. Refrigerant leaks can occur as a result of line connections degrading over time, severe vibrations weakening the refrigerant lines, or physical damage occurring to your unit. If your system is working occasionally, but can’t keep up during the hottest hours of the day, it may have a refrigerant leak. Longer cooling cycles are another sign of a possible refrigerant leak. Leaks might produce a hissing or gurgling sound during system operation. Hissing noises tend to indicate a small leak, while gurgling sounds signify a major leak. A sweet smell near the air conditioner may also be the result of a refrigerant leak.


7. Evaporator coil drain line clogged

Under your evaporator coil is a drain pan that catches condensate from the evaporator. This condensate then drains from the drain pan through a drain line, generally to a floor drain or a pump that pumps it to a drain elsewhere. This drain line can become clogged with mold, algae, dust, and dirt. A clogged line can cause the drain pan to overflow. A common sign this has occurred is standing water around your furnace or air handler. You might also notice water dripping from the drain pan at the bottom of the evaporator coil. Many systems have a sensor that trips when the drain pan stops draining. If your system shuts off and immediately switches off when you turn it back on it could be a sign that the drain line is plugged. A musty smell is another indicator of a clogged drain line.


8. Strange noises

Go to both the indoor and outdoor cabinets of the air conditioner and listen to the sounds from the system as it goes through a standard cooling cycle. Do you hear any unusual noises? Most air conditioning units produce a low-level hum, and this can be completely normal. However, if you hear something more, it warrants further investigation. A loud humming noise outside may be a defective contactor relay switch. Or the fan motor could be seized (unable to spin) but power is still going to it, creating resistance that produces a loud and noticeable hum. Faulty electrical components can produce a buzzing sound. A refrigerant leak can produce a hissing or gurgling sound. If your air conditioner is making a banging noise, this is an indicator of a problem with the compressor. If you hear squealing noises, that’s usually a belt problem. A screeching noise is often a malfunctioning outside condenser fan or inside blower fan. Grinding noises can indicate a motor problem.


9. Short cycling

Short cycling is when the air conditioner turns on then off before the desired temperature has been achieved throughout the house. If you believe your air conditioner is short cycling, listen to how long the air is running before it turns off. An air conditioner should run for about 15 to 20 minutes, then it should remain off for 7 to 10 minutes. This helps it cool off before starting another cycle. When it’s short cycling, it will be switching on and off in shorter bursts. There are several causes for short cycling. A dirty air filter may be creating poor airflow resulting in overheating. When your air conditioning system overheats, it will typically shut off on its own as a safety precaution. If your thermostat is located near an air conditioning vent or a window, it may not be correctly reading your actual home temperature. This too can result in your system starting up and turning off frequently. Try to have your thermostat placed near the center of your home and away from any doorways, windows and vents. Not having enough refrigerant in the system or a failing low-pressure control switch can also result in short-cycling. An oversized system will cool your home too quickly and then shut off in a short period of time. Short cycling results in excessive electricity use and puts extra wear and tear on your air conditioning system.


If during your test you encounter one or more of these, or other problems, and would like assistance with a solution, give us a call. We will be happy to help.


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