If you’ve noticed your central air conditioner turning on and off more frequently than usual, a problem known as short cycling, it can be a source of frustration and concern. Not only does short cycling strain your AC unit, but it also increases your energy bills and reduces the comfort of your home.
The cooling pros at Central Heating Cooling Plumbing Electrical in Kalispell have put together this list of potential causes and solutions, along with advice on when to call a professional for AC service.
How Long Should a Central Air Conditioner Run?
There is no single correct run time. It depends on the outdoor temperature, your house and how well the system is sized for it. A correctly sized air conditioner runs in steady cycles long enough to cool and dehumidify the house, and on the hottest Montana days it runs longer, which is normal.
If your AC shuts off after only a few minutes and starts again soon after, it is short cycling. A system that runs almost without stopping has a different set of problems, covered further down this page.
Common Causes of AC Short Cycling
1. Thermostat Issues
If your thermostat is located where it can be influenced by direct sunlight, drafts, or heat sources, it may incorrectly read the room temperature, leading to frequent cycling.
The solution is to move the thermostat to a more suitable location or replace it if it is malfunctioning.
See related: Where to Put Your Smart Thermostat Sensors
2. Oversized Central AC Unit
An oversized AC cools the house too quickly and shuts off before it finishes a full cycle. According to ENERGY STAR, short cycling increases wear and removes less moisture from the air, because less water condenses and drains off the coil. ENERGY STAR also found that lengthening a cycle from 5 to 9 minutes improved efficiency by 17 percent.
Consult with a professional to discuss possible adjustments or the need for a correctly sized replacement.
3. Dirty Air Filter:
A clogged air filter restricts airflow, causing the unit to overheat and shut down prematurely.
Check the air filter every month, and clean or replace it when it is dirty, as ENERGY STAR recommends.
4. Low Refrigerant Levels
Low refrigerant is another factor that can cause the AC to struggle in maintaining the set temperature, leading to short cycling.
Have a professional HVAC technician check for leaks and recharge the refrigerant.
5. Electrical Issues
Problems with the electrical connections or faulty wiring can interrupt the power to your AC unit intermittently.
Have a qualified electrician check the electrical connections to ensure they are secure and working safely.
6. Faulty Compressor
A failing compressor will struggle to maintain the pressure needed for proper operation, causing short cycles.
Have a skilled HVAC technician check the compressor. Depending on what they find, the compressor may need to be repaired or the unit replaced.
7. Iced Over Evaporator Coils:
When coils freeze, the AC will shut off to allow them to defrost, interrupting regular cooling cycles.
Look for ice on the indoor coil or on the larger copper refrigerant line at the outdoor unit. If you find ice, turn the cooling off, check the air filter and let the coil thaw. If it freezes again, call for service. See why an AC freezes up.
See related: Cleaning AC Coils
Quick Checks You Can Do Yourself
- Replace the air filter if it looks dirty.
- Make sure the thermostat sits in an interior room or hallway, away from windows, exterior doors and direct sunlight.
- Clear leaves, grass and other debris from around the outdoor unit so it can move air freely.
If the short cycling continues after these checks, schedule AC service.
When to Call a Professional for AC Service
While some solutions like replacing a dirty filter or moving a thermostat are simple DIY tasks, many causes of short cycling require professional assessment and intervention. Here’s when you should consider calling an expert:
Persistent Short Cycling
If the basic fixes don’t stop the frequent on and off, it’s time to call a technician. If possible, turn the air conditioner off until the unit is inspected to prevent damage and wear and tear.
Electrical Concerns
Electrical issues are not only tricky but also hazardous to address without proper training.
Refrigerant Leaks
Handling refrigerant requires certification due to its potentially harmful effects on health and the environment.
Compressor Problems
Due to its complexity and the importance of correct installation, compressor repair or replacement should be handled by professionals.
What If Your AC Runs Constantly Instead?
An air conditioner that rarely shuts off has the opposite problem. The most common causes are:
- A unit that is too small for the home. An undersized air conditioner struggles to reach the set temperature and runs almost continuously.
- A thermostat fan setting of On. With the fan set to On, the blower runs all the time, even between cooling cycles. Set it to Auto.
- Leaky ductwork. Gaps and holes let cool air escape before it reaches your rooms, so the system works harder. A technician can inspect the ductwork and seal it.
- A clogged air filter. Restricted airflow makes every cycle longer. Check it every month, and clean or replace it when it is dirty.
- An aging system. Older units lose efficiency as they age and run longer. A new, correctly sized air conditioner uses less energy.
- Air leaks and weak insulation. Gaps around doors, windows and walls let warm air in. Sealing them shortens run times.
AC Short Cycling FAQ
Is it bad if my AC keeps turning on and off?
Yes. The U.S. Department of Energy notes that frequent on and off cycling can wear out the compressor and fan controls. It also wastes energy and leaves the house more humid. If the quick checks above don’t fix it, turn the system off and schedule service.
Can a dirty filter cause short cycling?
Yes. A clogged filter restricts airflow, which can make the unit overheat and shut down early or let the coil freeze. Check the filter every month, and clean or replace it when it is dirty.
Can a thermostat cause an AC to short cycle?
Yes. A thermostat in direct sunlight, in a draft or near a heat source reads the wrong temperature and shuts the system off too soon. Moving it to an interior wall or replacing a failing thermostat can fix the problem.
Does an oversized AC short cycle?
Yes. ENERGY STAR says oversized air conditioners short cycle, which adds wear and reduces dehumidification. A correctly sized replacement solves it.
Remember, regular maintenance is key to keeping your AC running smoothly and efficiently.
At Central Heating Cooling Plumbing Electrical, we understand how vital a smoothly operating AC system is to your comfort and peace of mind. For 34 years we have been helping homeowners in Kalispell, Montana stay comfortable all year round.
Our Industry Certified Technicians are ready to diagnose short cycling and other AC problems, so your home stays cool and comfortable. Don’t let a malfunctioning air conditioner disrupt your comfort. Contact us today for AC repair in the Flathead Valley.
