Why does my AC work for 20 minutes then stops?

Author: Maximilian Gislason  |  Last update: Monday, April 7, 2025

Typically, short cycling can come from an incorrect unit size or programmable thermostat problems. However, it could also be caused by neglected routine maintenance or something that might require a simple repair.

Why does my AC run for 15 minutes then shut off?

If your air conditioner is turning on and off quickly, it may be short cycling. Short cycling is a serious problem that will almost always lead to the AC condenser outside your house wearing out more quickly if you don't repair the underlying problem. The compressor motor is always under lots of strain as it starts up.

Why does my AC run for a little then stops?

Several reasons could cause your air conditioner to keep shutting off, such as a dirty filter, low refrigerant, or a malfunctioning thermostat. To fix it, try cleaning or replacing the filter, ensuring proper refrigerant levels, and checking for thermostat issues.

Why does my AC turn on then off after a few minutes?

If your AC unit is turning on and then off right away, there are several possible causes. These include thermostat problems, refrigerant leaks, oversized AC units, and dirty air filters. With the exception of a dirty air filter, most of these issues should be addressed by a qualified HVAC technician.

Why does my AC stop cooling after few minutes?

Dirty air filters are usually the most common problem that air conditioners face. Faulty motors are another common issue that air conditioners face and that can impact the cooling system. If the AC stops cooling suddenly, the thermostat should be checked.

9 Reasons Why Your Air Conditioner Starts Then Stops Quickly

Why does my AC work for 30 minutes then stops?

Electrical problems are a common cause of short cycling. This may indicate that there is an issue with the electrical supply line or the capacitor could be broken or failing. This can be caused by the thermostat, electrical connections in the system, or the circuit boards.

How to tell if AC refrigerant is low?

Here are some of the symptoms of an air conditioner with low refrigerant:
  1. Takes Your AC a Long Time to Cool Off. ...
  2. Indoor Air Not Blowing Cool Enough. ...
  3. Frost or Ice on Copper Lines. ...
  4. Water Pooling Around the Furnace. ...
  5. Listen for a Hissing or Bubbling Noise. ...
  6. Short Cycling. ...
  7. Electric Bills Higher.

How to tell if a thermostat is bad?

A bad thermostat can be detected when your AC or furnace is not turning on, your HVAC systems are not turning off, the thermostat not responding, your HVAC system is short-cycling, the room temperature not matching the temperature displayed on the thermostat, and the programmed setting resetting themselves.

How to fix a short cycling air conditioner?

Fortunately, there are plenty of ways you can put an end to your air conditioner's short-cycling issues:
  1. Check your air filter. ...
  2. Check your thermostat placement. ...
  3. Check your air conditioner's refrigerant levels. ...
  4. Replace the low-pressure control switch. ...
  5. Check the compressor.

Why does my AC run for 2 minutes then shut off?

Your AC compressor may stop after a few minutes due to a clogged air filter or duct obstructions, which can cause the compressor to overheat and shut off the system prematurely. Ensure proper airflow by checking for dirty filters and obstructed ducts.

Why does my AC cool then stop?

Dirty or Frozen Coils

If the condenser coil is dirty, your AC can't complete the cooling process. It can cause the unit to malfunction and shut down whenever you turn it on. To avoid this, clean the condenser coil regularly. You can use a coil brush to clear debris and a fin comb to realign the coil fins.

How to know if AC is short cycling?

When your AC turns on, it will usually need to run for anywhere from 10 to 20 minutes to cool your home completely. If the AC turns on and quickly shuts off again within a couple of minutes, there might be a major issue causing your unit to short cycle.

How do you reset an AC compressor?

Most air conditioners come with a reset button attached to the compressor unit. Typically, it is a red button and is very visible to an onlooker. To reset your air conditioner, all you have to do is press the button, and you won't have to worry about all the heavy lifting.

Why does my AC run for 10 minutes then stops?

Electrical and wiring problems that are causing your AC unit to short cycle could include loose or corroded electrical connections. This can lead to temporary power loss from your air conditioner if not repaired. Make sure to contact a technician to repair your system if you notice this problem.

Why does my AC turn off every 30 minutes?

A common reason for a short cycling AC system is electrical problems. This may be caused by a bad connection, a broken thermostat, a faulty circuit board, a condenser or compressor not receiving power properly. To properly diagnose and repair the electrical issue, call a licensed HVAC contractor.

What does short cycling mean?

In the heating, ventilation, and air conditioning (HVAC) business, short cycling is a phrase used to describe when a heater or air conditioner cycles on and off too frequently. It signifies a problem in your heating system's proper functioning and efficiency, in which it is not completing its heating processes.

Can a thermostat cause AC to short cycle?

Several issues can cause short cycling, such as an oversized HVAC system, a clogged air filter, or a malfunctioning thermostat. Low refrigerant levels or a blocked evaporator coil can also force the system to shut down prematurely.

How much does it cost to fix a short cycling AC unit?

Central AC Short Cycling

Homeowners spend between $75 and $600 to deal with short cycling issues in their central AC systems.

How do I know if my AC compressor is shorted?

In order to verify, you will need to scratch the paint off the side of the compressor to bare metal. Set your DMM to the highest ohm (Ω) value. Place one meter lead on the bare metal and the other across C, S and then R. If there is a short, there will likely be little resistance to ground, typically 1-2 Ω's.

How do I manually test my thermostat?

Standard thermostats: Enlist a friend or family member to assist, Position one person by the thermostat and one person by the furnace. Slowly turn the thermostat from off to heat and increase the temperature. Both the thermostat and furnace should make a sound.

How to reset a thermostat?

Most modern thermostats will have a clearly marked reset button inside the panel. It's usually small and recessed, so you might need a pointed object like a paperclip to press it. For those wondering specifically how to reset air conditioner thermostat models, the process is generally the same.

How do I know if I need a new thermostat?

If your thermostat has fresh batteries but suddenly lacks power, flashes, or isn't responsive to adjustments, it may need replacement. If resetting the thermostat doesn't resolve the problem, you may have wiring problems or faulty components causing your thermostat to not turn on.

How often does AC need Freon?

Well, Most systems can get by with Freon replacement every two or five years. However, the most significant exception to this rule is when there is a leak in the air conditioning system, which decreases the amount of the refrigerant in the AC unit over time.

Why is AC not blowing cold air?

First, check your filters and coils for dirt and debris that may be impeding airflow. Once you've cleaned the filters and coils, run the air conditioner with just the fan so that the ice accumulation can melt off. If the AC still doesn't blow cold air, it could be that refrigerant levels are too low.

Can AC be low on Freon without a leak?

While the refrigerant in your vehicle can escape even without a leak, it's often not enough to cause significant issues unless you've failed to top up the refrigerant for years. When the lack of refrigerant becomes significant though, it can cause a number of problems, including an overheating driver in the summer sun.

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