Why Is Your AC Not Working? The Leading Reasons Why Air Conditioners Malfunction

Air conditioner repairman in uniform and a clipboard.

During the summer months, air conditioning can be a game-changer. Sometimes, however, your unit might stop functioning correctly. This can be a major inconvenience when June rolls around. Find out what might be causing your air conditioning problem, as well as easy ways to prevent, and even reverse the damage.

We recommend, especially with those handling the scorching Texas summers, to bring in professional HVAC service if you have little expertise in air conditioners. Nowadays, AC units have a degree of complexity that makes them harder to fix, unless you have a diagnostic background. Additionally, yearly scheduled maintenance may prevent future issues and may extend the life of your unit.


The most direct place to start when trying to narrow down an AC malfunction is the thermostat. It may have been wired incorrectly, particularly if it has been recently replaced. A common indicator of thermostat errors is a lack of air escaping the vents. This problem shows up frequently, however, is often easy to manage. If you have a programmable thermostat, it may have been programmed incorrectly. Refer to the instruction manual to reset the thermostat.
Another common problem which often remains overlooked is your thermostat’s batteries. Replacing them may be all you need to restore proper cooling to your home.

Air Filters

The most common reason for faulty AC units is a neglected air filter. While these filters are meant to be replaced frequently, many people forget to change them more than once or twice per year. If yours shows signs of buildup or wear and tear, replace it immediately.

Condenser Coils

Check your condenser coils: Your outdoor air conditioning unit works by drawing in surrounding air through the sides, later cooling incoming air and disposing of the hot air through the top grate. During this process, the coils in your unit can become extremely dirty and covered by foliage, dust, cottonwood seeds, etc. Make a point of cleaning them once a year. This step is easy; all you need is your hands or a hose.


Check the outside unit for mice nests or corrosion. This is a fairly common problem and will require removal of the cause as well as replacement of any chewed or damaged components

Fan Blades

After a long period of time, the blades of the fan as seen through the top of your unit can become difficult to rotate. Using a pen or similar object, reach through the top slats of the unit and spin the fan. If the blades do not rotate freely, remove the grate. The fan will be attached. Flip it upside down with the fan blades facing towards the sky. Find the axle or oil ports of the fan and apply the oil directly to them. Oils with a spout for easy application is recommended. It is also beneficial to clean this part of your unit at least once a year. Keeping your fans well maintained and clean can prevent damage to the compressor.

Compressor Problems

If your air conditioner is making loud, clanking sounds, the problem is probably the compressor, located inside the unit below the fan. Generally, these loud noises indicate the compressor must be replaced. This is an expensive repair, costing upwards of $1200. As a result, many people choose to replace the entire air conditioning unit as an alternative to costly maintenance.


If every component appears to be working, however, the air inside your house is still not cooling, it is likely due to the refrigerant inside your unit. Air conditioners are closed systems. This means that unlike the gasoline in a car, the refrigerant originally placed in the unit will recirculate continuously throughout its life. If it is depleted, there is a leak. Leave this particular problem to a professional, as refrigerant requires a license to purchase and experience to replace.

Keep in mind that any professional replacing the refrigerant in your air conditioner should also patch corresponding leaks. It is also important to note that the most common type of AC Refrigerant-Freon, is quickly being phased out by R-22. However, it is estimated R-22 will also be replaced by 2020, in favor of more environmentally conscious alternatives. If purchasing a new unit, be sure it uses a contemporary refrigerant.


The moisture which is removed from the air prior to being released is fed through a drain line prior to reaching the drain. This drain line can become coagulated over time, causing the water to back up and eventually overflow. This will be damaging the exterior of your unit, as well as surrounding drywall and furnishings. Compressed air is a common and effective solution for clearing the blockage.

Evaporator Coils

The coils responsible for cooling the air prior to discharging it into your home are filled with refrigerant. However, they require warm air circulation in order to prevent a buildup of ice on the coil exterior. If this occurs, your unit will be unable to effectively cool airflow, and you will experience warm air escaping your vents.

In order to establish this problem, check your unit for ice and condensation. Often times, frozen evaporator coils are caused by a disruption in airflow. Check your filter to establish it is not blocking airways, then give your unit time to thaw. Also, be sure to clean your coil’s interior, as dirt buildup can be disruptive to the heating and cooling process.

Air Ducts

While the air conditioner is responsible for cooling the air in your home, the air ducts inside your walls are responsible for distributing it. If these ducts have leaks, the cool air from your unit will be released inside the walls. Not only does this negate the purpose of air conditioning, but it also forces your unit to work harder to bring the temperature of the building down. In order to establish leaks, turn your air conditioner on, then feel along the ducts for escaping air. Once a leak is located, you can use foil tape, specifically designed for air ducts, to block the leak. Follow this up with a layer of duct mastic over the tape, creating an effective seal. This will restore the efficiency of cool air dispersal and prolong the life of your unit.

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