When your whole-house air conditioning system stops working

When your whole-house air conditioning system stops working, it can be frustrating—especially during the hottest times of the year. Fortunately, most issues come down to a handful of common problems that HVAC technicians see all the time.

One of the first things to check is power. If your system won’t turn on at all, it could be something as simple as a tripped circuit breaker or a blown fuse. Sometimes, the issue is the thermostat—dead batteries, faulty wiring, or incorrect settings can make it seem like the system is broken when it’s really just not getting the right signal.

Another common cause of AC problems is low refrigerant, often due to a leak. Refrigerant is the substance that cools the air, so if it’s low, your system might blow warm air or struggle to cool the house. If you notice ice on the lines or hear a hissing noise, that could point to a leak. In these cases, a licensed technician will need to find and repair the leak and then recharge the system.

Speaking of ice, a frozen evaporator coil is another frequent issue. This usually happens when airflow is restricted—often because of a dirty air filter—or if there’s a refrigerant issue. If your system is running but not cooling, and especially if you can see frost on the indoor unit, turning it off and calling a pro is a good idea.

Dirty air filters might seem minor, but they can cause a surprising number of problems. A clogged filter restricts airflow, makes your system work harder, and can even lead to overheating or freezing of coils. Regularly changing your filter (every 1–3 months) is one of the easiest ways to prevent problems.

Sometimes, the issue lies with the outdoor condenser unit. If it’s dirty or clogged with leaves, grass, or debris, heat can’t be expelled properly, and your AC won’t cool efficiently. Giving it a good cleaning can make a big difference.

Then there are the electrical components, air conditioning repair like capacitors and contactors, which help power the fan and compressor. If one of these parts fails, the system might click but not start, or it may start and shut off quickly. These parts wear out over time and typically need to be replaced by a technician.

In some cases, the issue might be a clogged condensate drain line. If the line that removes moisture from your system gets blocked, water can back up and trigger a safety switch that shuts the system off to prevent damage. Clearing the line and resetting the float switch can usually get things running again.

Finally, if you’re noticing poor airflow or no air at all, the blower motor or fan might be the culprit. These parts move the air through your home, and when they fail or wear out, you’ll usually notice uneven cooling or complete airflow loss.

If your AC isn’t working right now and you’re seeing one or more of these symptoms—warm air, no airflow, strange noises—it’s a good idea to turn off the system to prevent further damage and call a qualified HVAC technician. Most problems can be diagnosed and repaired quickly once you know what you’re dealing with. Would you like help troubleshooting a specific issue you’re having right now?