The AC compressor, also known as a condenser, is the unit that sits outside your home and supplies cold refrigerant to the inside part of the system. If the compressor stops working for any reason, you obviously won’t have any air conditioning. The compressor can simply fail because of age, in which case your only option will be to replace it. However, many other issues can also prevent the compressor from turning on, some of which are things you may be able to fix on your own. If you ever face a situation where your AC compressor won’t work, here are the steps you should take.

Check the Circuit Breaker

Air conditioners can sometimes have electrical issues that cause them to occasionally trip the circuit breaker, and the breaker can also trip because your home experienced a power surge. For this reason, the very first thing you’ll want to do is open your main electrical panel to check if the circuit breaker is tripped. If the breaker is tripped, you should first shut your AC off at the thermostat before resetting the breaker, as otherwise, the circuit could get overloaded and trip the breaker again.

Even if the breaker isn’t tripped, resetting the circuit is sometimes all it takes to get the compressor running again. To do this, you’ll again want to turn the system off at the thermostat. You can then flip the breaker off and then wait a few seconds before turning the breaker back on to reset the circuit.

Many AC compressors are installed so that there is also a power switch located on the exterior wall near the unit. If your system is designed this way, it’s also a good idea to make sure that the switch is set to on as there is always a chance someone flipped the switch off.

Test Your Thermostat

After checking the circuit breaker, you want to troubleshoot for thermostat issues. If your thermostat has batteries, replacing them is a good idea. The batteries are usually just a backup so that the thermostat settings don’t get reset if there’s a power outage, but some thermostats also use battery power to signal the AC system to run.

After replacing the batteries, try turning the temperature setting on the thermostat down a further 10 degrees. If the compressor now runs, it means that your thermostat isn’t calibrated properly, and you’ll need to have a technician either recalibrate or replace it.

You should hear the thermostat make a clicking sound when it signals the system to run. If the thermostat repeatedly clicks and nothing else happens, it usually indicates a problem with the thermostat wiring.

If the compressor still doesn’t turn on, try turning the thermostat to heating to see if your furnace will come on. If the furnace does come on, you can rule out the thermostat as the cause of your AC issue.

Replace Your Air Filter

The next step is to replace the AC air filter, which should be located in the ductwork that leads to your furnace or air handler. You should always change or wash your air filter every 30 to 90 days, or else it can become clogged and create numerous issues, such as your evaporator coil freezing up or the blower motor overheating. If the blower motor does ever overheat, it can trigger a switch that will prevent the AC system from running until the motor cools off.

After replacing the air filter, wait around an hour and then try to turn your AC back on. If the compressor now runs normally, you can be pretty certain the issue was related to a dirty air filter.

Make Sure the Condensate Drain Pan Isn’t Full

The next step is to open up the access panel on your air handler so you can inspect the condensate drain pan. Depending on how the system was set up, you may need to remove a few screws to gain access to the air handler. You should then see a metal or plastic pan that sits directly underneath the evaporator coil, and you’ll want to ensure the pan isn’t full of water.

Most all AC systems have a float switch inside the drain pan that works to ensure the drain pan shouldn’t ever overflow and send water leaking everywhere. If the water in the pan ever rises above a certain level, it will trigger the switch and automatically shut the entire system down. When this happens, nothing will run until the drain pan is empty and the switch can reset.

If the drain pan is full, it indicates a clog somewhere in the condensate drain system that prevents the water from draining away as it should. In this case, you will usually need to have a technician clear the clog so the system will then drain. While you can get the system working again on your own by vacuuming or soaking up all of the water in the drain pan, it won’t take long before the pan fills up and the system shuts off again.

Reset the Blower

After checking the drain pan, you can also try to reset the blower motor. This is also located in the air handler compartment, and you should see a red button somewhere on the motor. Before resetting the motor, make sure the system is shut off at the thermostat. You can then hold the button on the blower motor in for at least 30 seconds to reset it before turning the system back on to see if the compressor will now come on.

Listen to the Compressor When It Tries to Start

This last step before calling a technician is to listen to the compressor when it tries to start, as this can at least help you pinpoint the issue. This will require the help of another person as you will need them to be inside to turn the system on at the thermostat while you stand outside and listen to the compressor.

If you hear the compressor click repeatedly, it indicates that the AC capacitor is malfunctioning or bad. All AC compressors require a huge energy source to turn on, and the capacitor acts like a battery to supply the extra power needed for the unit to start. If the capacitor is bad, you will also often hear the compressor make a loud humming sound as it tries to start. This sound results from the compressor motor trying to start on its own without the extra power from the capacitor.

If you hear a single click and nothing else, it most likely means that the AC contactor is bad. The contactor is what receives the signal from the system’s main control board and relays it to the compressor. The good news is that repairing or replacing the AC contactor or the capacitor is fairly simple.

If your compressor still won’t work after trying all of these steps, it is now time to call in the help of a professional AC technician. The problem could be related to a faulty control board or numerous other issues, and the only way to find out what is preventing your compressor from working is to have the system inspected.

At Air 24/7 Air Conditioning & Heating, we can help if you need an AC inspection or any other HVAC service. We specialize in repairing and maintaining all types of heating and cooling systems, and we can also assist with any installation or indoor air quality needs you have. For more information or to schedule a service call in the Tampa area, contact us today.


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