4 Reasons Your AC Is Not Working (2024)

The first thing most people do when their AC stops functioning is check their thermostat. There are three main reasons why your thermostat would be off.

1. The batteries in your thermostat died. Dead batteries are an easy fix. Some thermostats have a front battery cover; for others, you have to pull the thermostat off the wall to access the batteries. Either way, replace the batteries to see if they were the culprit.
2. You have a tripped breaker or a blown fuse. A tripped breaker or blown fuse in the AC circuit is not uncommon on a hot summer day. If you have a tripped breaker, make sure you turn it off and then on to reset it. In contrast, a blown fuse requires replacement. However, if the breaker trips or the fuse blows again, there are electrical issues, and you need to call a professional electrician.
3. The primary drain line is clogged. A clogged drain line is one of the most common problems with a cooling system. Air conditioning units are constantly producing condensation. As warm indoor air moves across the cold indoor coils, condensation forms. This condensation is drained outside through a drain pipe. These pipes or the drain pan have a float switch to turn off the unit in case of a clog. This prevents water damage.

It is a bit counter-intuitive, but ice build-up should not be on any of your AC components. If your air conditioner is not working, isn’t working well or you have low airflow, check your AC components for ice build-up. This includes the outdoor unit, the indoor air handler and the refrigerant lines. There are several possible causes for ice build-up.

1. Dirty air filters
2. Dirty coils
3. Too many closed vents
4. A dirty or faulty fan motor
5. A refrigerant leak or low refrigerant levels

The first four issues will reduce airflow across your evaporator coil. If less warm air moves across your evaporator coil, the coil will get too cold and freeze the condensation that forms on it. Luckily, you can take care of most of these issues yourself.

It is important to note that you should never close vents in unused rooms. Although it might seem like you’re wasting energy by cooling unused rooms, closing vents can waste more energy and damage your system.

A hot room will simply pull in the cool air from the surrounding spaces. Additionally, closing vents can build up pressure in your ducts, reduce open vents’ airflow, or possibly damage your fan motor. Keep all the vents in your home open, so the system operates as intended.

If you replace your filters, clean your coils and open all your vents and your system is still iced up, then it’s likely a bad fan motor or low refrigerant. Both of these issues will need to be diagnosed by a professional.

Capacitor replacement is probably the number one service call for HVAC technicians. When your thermostat calls for AC or heat, the capacitor provides the initial 240 volts to start the compressor and fans. Capacitors last about five to 10 years, so you will end up replacing one to three capacitors over the life of your system.

Although some homeowners can tackle the job themselves, most call in a professional. The good news is that it’s not an expensive job. The average cost to have a capacitor replaced is $150 to $400.

Being in a hot home can be miserable and sometimes dangerous. If your AC quits, there are certainly some repairs you can handle on your own. You can save money and time by learning about your system, the common issues and the simple repairs.