An outdoor AC unit typically stops running due to a tripped circuit breaker, a blown fuse, a malfunctioning start capacitor, or a clogged condensate drain that triggers an emergency shut-off switch. In some cases, the system simply needs to be reset at the main power disconnect.
The unit won't turn on when you don't have enough refrigerant, and an HVAC tech will need to analyze the system to see what's going on. You might just need a refrigerant recharge. Or, if you've got a leak, your tech might need to perform a leak search. In some cases, you'll have to replace the system.
If the thermostat is not reading the temperature correctly or is stuck in heating mode, it may prevent the outside unit from turning on, even though the inside system is still running. Solution: Check the thermostat settings to ensure they're accurate and try resetting it or changing the batteries.
How Do I Reset My AC on My Own?
Power down your AC: Turn off your AC unit and unplug it from the power source. This will ensure that you stay safe while working on the unit. Locate the reset button: Most air conditioning units have a reset button located near the outside unit. It is usually a small button located inside a small hole.
An air conditioning (AC) unit typically lasts between 15 and 20 years. However, this AC unit lifespan can vary significantly based on factors like routine maintenance, daily usage patterns, installation quality, and your local climate.
The 3-minute rule is a simple but important guideline: wait at least three minutes after turning your air conditioner off before turning it back on. That short pause gives the refrigerant pressure in the system time to equalize.
If you notice your AC isn't turning on or is failing to cool properly, turn off the system and allow the coils to thaw completely. A dirty, clogged air filter is a common cause of frozen indoor coils, so be sure to replace your filter every three months to maintain proper airflow.
The indoor unit responds directly to your thermostat, but if the outdoor unit has a power problem, a failed component, or a tripped safety switch, it won't respond. Common causes include tripped breakers, failed capacitors, contactor problems, and low refrigerant triggering a safety shutdown.
The short answer is yes; you should turn off your AC unit if it's not cooling. Leaving your AC unit on when it's not cooling can lead to further damage to the system, resulting in costly repairs or even replacement.
Signs Your AC Fuse May Be Blown
Why is my outside AC unit fan not running while my inside unit is blowing air? The outside fan may not run due to various issues, including power problems, a tripped breaker, or a blown fuse. Malfunctions in the capacitor and relay can also stop it.
How to Fix Your Outdoor AC Unit Step-by-Step
Simply put, it means you should never set your thermostat for a temperature more than 20 degrees cooler than the outside air. Why not? Most air conditioning systems can only handle a 20-degree difference between the outside and inside air temperatures.
Ideally, your air conditioner should cycle 2-3 times an hour to maintain a consistent temperature throughout your home. On those warm days, expect your AC to run for about 15 minutes each cycle. During extreme heat, your AC might need to work almost continuously to keep your space cool.
Click and hold the reset button for three to five seconds. Restore power to your AC by flicking the circuit breaker back on. Finally, set the thermostat to “cool” and set it to a temperature slightly colder than the current indoor temperature. The air conditioner should come to life in just a few seconds.
However, replacing the outdoor unit will typically fall in the $6,000 – $8,000 range, which is over half the cost of some full air conditioning systems. So, while it's true that you'll see some short-term savings, the chances of a partial replacement's benefits outweighing the long-term costs are very low.
Which AC brand lasts the longest in 2026? Historically, Lennox, Trane, and American Standard lead the industry in longevity. With proper maintenance, these units can last 15–20 years.
The short answer: Definitely not. (Unless you have manually engaged your outside fan to run constantly, but it shouldn't be running for hours on it's own.) If your HVAC is functioning correctly, it should keep your house cool by cycling on for 15-20 minutes at a time—with distinct pauses in between each cycle.
To reset your air conditioner, turn off the thermostat, press and hold the reset button on the outdoor unit for 3 to 5 seconds, then release. Wait a minute before turning the thermostat back to cool. If problems persist, call a licensed HVAC professional to receive assistance.
Locating the Reset Button
To find it, you should first turn off your HVAC system to ensure safety. Remove the thermostat cover by either snapping it off or unscrewing it, depending on the model. Most modern thermostats will have a clearly marked reset button inside the panel.