If your air conditioner does not cool properly, there are four basic troubleshooting steps you can easily perform for yourself. First, check the thermostat settings, just to be sure it wasn’t accidentally switched to heat instead of A/C. While you’re looking, check the fan settings, too. When the fan is set to the “On” position, it will blow even when the A/C unit isn’t running. It can make you think something is wrong because sometimes it blows cold air, then it goes back to blowing warm air. Set the fan to “Auto” to make it come on only when the A/C kicks in. If you find the settings are correct, take the next step to find the problem.

Check the air filter. A dirty filter obstructs the flow of air that needs to flow over the evaporator coils. The unit draws in the warm air inside your house, but the air can’t get past the dirty filter to be cooled. Go to your fuse box and shut off the power to the A/C system for your personal safety. Remove the dirty filter and either clean it or replace it. If you don’t have a replacement filter, write down the size so you get the buy the right one. They come in lots of sizes and types, so taking a picture with your smartphone is also a good idea if you are new at this. Once you put in a clean filter and restore power, you should feel the difference immediately. If this is not the problem, you must do a more thorough check of the unit.

When the Freon, or other refrigerant, charge is low, the A/C can’t cool the air. If this is the case, there is a leak somewhere. The main signal that your unit has a leak is that the A/C cools the house just fine when the weather is cooler, such as night time or cooler days, but not on hot days. Another sign of low Freon is an ice buildup on the refrigerant coils and the outside unit. Also, with the power off, if you hear any hissing or bubbling sounds in the unit, that’s a leak. Leave the system off and call a professional service before you turn it back on. Trying to use the system like this will damage the compressor beyond repair. Lacking the signs of a leak, there’s another problem to consider.

Your air conditioner may be near the end of its operational lifespan and just cannot cool your house the way you’re used to it doing. Getting the system checked by a professional is important when your troubleshooting efforts do not solve the problem. You may need to have the system serviced, repaired, or even replaced when it can no longer do its job effectively.