Make sure the outside unit is turned on (there's probably a switch near the unit). If the outside unit has a separate circuit breaker, check your circuit box and make sure it hasn't been tripped. A more serious issue if the outside air conditioning unit's not working is a broken compressor, capacitor or fan.
The main reasons your AC unit outside is not turning on could be something that has tripped the circuit breaker, something is blocking the fan's airflow, or the condensing unit is damaged. Other potential issues could be the thermostat isn't set correctly or the compressor could be malfunctioning.
When the outside unit breaks down but the inside unit is running, the culprit may well be a broken compressor in the outside unit. That's typically a major repair, something that might even warrant a system replacement.
It's a small, red button usually located on or around the unit. The button should have a clear 'reset' label. Once you find the button, press it for around three seconds and observe the AC. Check whether the AC kicks on immediately and if it doesn't, press the button again for another three seconds.
The outside AC unit may not function effectively if one of the fans is compromised. You can identify if the blades in your AC unit are spinning by listening for a humming sound. Your AC condenser fan may not turn due to power issues, a burnt-out motor, a worn-out capacitor, or a faulty compressor contactor.
As for the outdoor AC fan, it blows air over warmer refrigerant to remove the heat and keep the system cool. If one or both fans aren't spinning, your HVAC system can't run properly.
A condenser that won't come on could have a variety of problems, because there are many issues that would prevent activation. The wiring might be wrong, a motor might be faulty, the compressor could have gone bad, or it is completely out of refrigerant. Might even be a problem with the thermostat.
If your outside AC unit is not turning on, it could be a thermostat issue. If your thermostat clicks but the AC does not turn on, you could have an issue with the thermostat itself. Broken thermostats often fail to properly communicate with the rest of your heating and cooling system.
Shut off your system by hitting the isolation switch, wait 30 to 60 minutes and then turn it back on. This manual reboot fully disconnects your AC unit from power, allowing all electrical components to reset.
FIND THE RESET BUTTON
In most cases, the small red reset button is inside the AC's compressor. If unsure, you can always refer to the user's manual to find the exact location.
If you think your air conditioner has blown a fuse, the first sign you'll notice is that the outside AC unit is inoperable. The best way to check for a blown fuse is by using a voltmeter. Be warned — you are working with live electricity and should use extreme caution when troubleshooting your system.
A central AC system consists of indoor and outdoor units. An indoor air handler can continue running when the outside unit has shut down. While air will blow from the vents, it won't be cooled; it may be as warm as the summer air outside.
This can happen if the system is set to "fan only," causing only the inside fan to circulate air without engaging the outside unit to cool the air. Other thermostat settings that can lead to similar problems include incorrect time or day settings, or an unresponsive touch screen.
A sure sign of a bad AC capacitor is a humming sound from within the access panel. Any humming noises indicate a problem with the air conditioning system or the components of the AC unit. Try turning the power on and off again to see if it was a one-time issue with the motor or a recurring problem.
No, most outside units have a timer where the compressor waits for 5 minutes before coming on. It gives the refrigerant time to equalize so the compressor doesn't have to work as hard to start up.
If You Don't Have a Reset Button on Your Outdoor Unit
Unplug the unit from the power supply board and disconnect the system. This ensures that the AC unit is receiving no power whatsoever. Wait 30 minutes, then plug the unit back in.
In general, wall and window air conditioning units with smaller capacities can typically run for up to eight hours at a time before they need to rest. Larger wall and window units have a longer running time of around 10 to 12 hours, depending on their cooling power.
If your AC is running but not cooling, it could be due to a dirty air filter, incorrect thermostat settings, a malfunctioning thermostat, a refrigerant leak, dirty condenser coils, blocked vents or ducts, a faulty compressor, frozen evaporator coils, or electrical issues.
To unclog an AC drain line, turn off the power to the unit. Locate the drain line and use a wet/dry vacuum to suck out the clog. Flush the line with water using a garden hose or cup of water. Check and clean the drain pan under the indoor unit.
Typically, you can find the switch for the indoor unit near your system's furnace or air handler. You can find the switch for the outdoor unit next to the outdoor unit, usually in a metal box on the exterior of your home.
As mentioned, one of the more common reasons for an AC unit needing a reset is due to the protection circuit breaker inside the unit kicking in. This usually happens after a power outage occurs, and this failsafe is in place to prevent fires and explosions from occurring from a power surge.
For AC capacitor replacement, anticipate spending between $150 and $400, depending on the capacitor's type and accessibility. A bad AC capacitor is a fairly minor repair, and most HVAC technicians will recommend a repair rather than replacing the unit when the capacitor is the problem.