How to Check Your Air Conditioner Before Calling for Service

What do I check if my air conditioner shuts off by itself?

Check the circuit breaker to see if it's been tripped. If you’ve got too many electronics plugged in and running, you may have overloaded the circuit. This is especially likely if you’ve got a bunch of fans running during a hot summer day. Check your fuse box to see if the circuit breaker is set in the off position and flip it back on. If everything else shut down at the same time, you may simply be dealing with a power outage.

Check the auto settings on your thermostat. If your air conditioner keeps kicking on and off in intervals, look at your thermostat to see if it’s set to “auto” or “automatic.” If it is, this is why your AC keeps shutting off. When it’s set to auto, the AC system will only turn on after the temperature has risen past the number on your thermostat. It’s much more efficient to keep the thermostat set to “auto” when you’re heating or cooling your home. Still, if it isn’t warm or cool enough for you, feel free to adjust the thermostat!

My thermostat won't turn on. What should I do?

Replace the thermostat's batteries and see if it comes back on. Read your instruction manual to see how you take the faceplate off. In most cases, there’s a small lip on the cover and you can just pry it off by hand. Replace the batteries in your thermostat and put the cover back on to see if that resolves the problem. If there are any electrical issues, you won’t be able to fix those on your own. Call an electrician or HVAC technician to have them take a look at the problem.

My AC turns on but the airflow is messed up. What do I do?

Change the air filter. Your filter needs to be replaced every 3 months or so. During the hot season, you may need to replace it every month. If you’ve got a problem with your AC unit and you haven’t replaced the filter in a while, do that first. If the problem resolves itself, you don’t need to call anyone. If the problem persists, you’ll probably need to call an HVAC technician. On a central AC system, the filter is usually located in the duct on the return line, or on the furnace. In a ductless system, there’s a reusable filter on the condenser outside. For a window unit, the filter is usually behind the grates on the front.

Check your vents and ducts for blockages. If there are any obstructions in front of the vents or ducts, this could disrupt your system’s ability to function correctly. Take a stroll around your home and make sure all of your vents and ducts are clear and open. If necessary, rearrange your furniture to make sure that everything is open. If there is any debris outside around your condenser unit, clear it away. This can occasionally be the source of the problem.

What do I check if my AC turns on but isn't blowing cool air?

See if the air filter is dirty and change it out. Swapping out your air filter may help. A dirty filter can mess with an AC unit’s ability to blow out cool air, so try this first to see the problem resolves itself. If you have a reusable filter, clean it thoroughly before replacing it.

Inspect the refrigerant line. On a central or split system, go outside and look for the largest pipe leading into your AC’s condenser. If your AC is on and this pipe has ice on it, shut your system off and give this pipe time to thaw before turning it back on. If this problem occurs again, you may be running low on refrigerant.

Clean off the condenser coil on the outside unit. Head outside and remove any garbage surrounding the condenser. If anything is stuck in the fins, remove it by hand or with a broom. Then, grab a hose and gently spray down your condenser unit. Keep rinsing it until the water runs clear. Dirty coils can occasionally disrupt the airflow and make it feel like your vents are blowing out warm air. You can clean the coils on a window unit as well, but you’ll need to take it outside to do this.

My AC is acting strange. How do I reset the unit?

It sounds oddly simple, but you turn it off and turn it back on again. Turn your AC off at the thermostat and then use your instruction manual to locate the power button. Press that to shut the AC system down. Then, go to your circuit breaker and flip the breaker for your AC unit off. Wait 1 minute, and turn the breaker back on before restarting your AC unit. It often helps to do this if you accidentally tripped a fuse or you just had a power outage and your AC is acting funny. However, if you have to do this frequently, it’s a sign that something may be going on with your system and you should get an HVAC pro to take a look at it.

Is it necessary to have a pro service my AC every year?

Yes, even if it seems like there’s nothing wrong. You still need an HVAC technician to come out and service your AC system at least once a year just to keep minor issues from becoming major problems. An HVAC pro will clean your system, check for leaks, and make sure that everything is in working order. This is the best way to make sure that any potential problems get resolved.

Which issues are too dangerous to troubleshoot myself?

Anything involving leaks or opening the AC unit up is risky. While it’s perfectly fine to take a look to try and find a problem, you really shouldn’t mess around with your AC unit too much. You won’t be able to diagnose anything going on inside of the condenser or furnace, and opening them up may void your warranty or make things worse. Freon and other refrigerants can be toxic, so don’t mess around with any leaks or fluids in your AC system.

Messing with the electrical components is especially dangerous. AC systems are typically high voltage, and it’s dangerous to toy around or touch any live connections. There are a variety of problems that look like a blown fuse, but aren’t. On top of that, you won’t be able to fix any of these problems yourself, so it’s just going to be more efficient and safe to have a professional take a look. You can theoretically check the cartridge fuses on an AC system with a multimeter, but it won’t necessarily tell you much and it’s dangerous. A professional will be able to check the fuses in 30 seconds anyway, so there isn’t a particularly good reason to check them yourself.