If your AC keeps turning off and on more than it should, you’re probably experiencing short cycling. It happens when the AC unit switches off before it finishes a full cycle, leaving the temperature around the house slightly off. It’s a subtle issue, with symptoms being uneven temperatures and an AC that seems to be running too much or too little.
Short cycling can impact your AC’s efficiency, driving up your energy bills over time and causing unnecessary wear that will eventually call for repairs. Learn more about it, including common causes and how to fix short cycling.
What Is Short Cycling?
To understand short cycling, we must first understand what a cycle is in heating, ventilation and air conditioning (HVAC) terms. A single cycle is when your air conditioning system turns on, cools the space until it reaches the thermostat’s set temperature, and then shuts off.
AC short cycling occurs when the system shuts off before reaching the set temperature. It can occur for various reasons. Fundamentally, it happens because a malfunctioning component inside the AC interrupts its normal function, causing it to switch off — and then automatically switch on again because the room is not at the right temperature according to the thermostat.
The increased frequency of the AC turning on and off means it uses more power than a normal, uninterrupted cycle, leading to more electricity usage and reducing overall efficiency as it runs.
What Causes Short Cycling?
There could be a few common reasons why your AC keeps turning on and off:
- Dirty air filters or condenser coils: Dirty components restrict airflow, which could lead the system to overheat or the evaporator coil to freeze. The AC’s built-in safety measures will cause it to shut off. Once the system has reached equilibrium again, it will restart.
- Electrical issues: Bad wiring, a malfunctioning control board or faulty relays will disrupt the electrical signals the AC needs to function, causing system restarts.
- Refrigerant leaks: Refrigerant is responsible for heat absorption and conversion into cool air. When the refrigerant is low, the system can overheat. The low pressure can also trigger a shutdown.
- Incorrectly sized AC units: Most commonly, the unit is too large for the space, causing it to cool the area too quickly and shut down before a full cycle is complete.
- Thermostat malfunctions: Your thermostat could be faulty or located in a spot where reading the temperature is difficult, causing it to signal the AC to shut off before it reaches the desired temperature.
How to Fix a Short Cycling Air Conditioner
You’ll know you’re experiencing this issue if there are inconsistent temperatures throughout your home, or you’re always feeling that the temperature is too warm. To troubleshoot effectively, follow this short step-by-step guide.
1. Clean or Replace the Filters
The first thing to do is check an easy-to-reach component — the air filter. Turn off the unit and use the manufacturer’s guide to locate the filter. Most are easy to remove by sliding them out or using a screwdriver. You may need to replace the filter. First, try cleaning it to see if it’s reusable.
2. Check the Thermostat
If cleaning the filters has no effect, the next step is to check your thermostat. If it’s located near a heat source like direct sunlight or close to air vents, that could be why it’s misreading the temperature. In this case, moving it should solve the issue.
If placement isn’t a problem and your thermostat isn’t hardwired, try replacing the batteries. You should also verify that the settings are correct. Conduct tests with a range of temperature readings to identify if the AC turns on when it’s supposed to. If it doesn’t, it’s likely time to call in a professional to replace it.
3. Consider the Sizing
This step requires a few calculations to determine if you have an oversized or undersized unit. Look at your AC capacity in the specifications for your model. You can then compare the unit size to your home’s square footage. Your manufacturer’s guidelines for your model should have a chart to compare square footage and AC capacity. However, it’s best to call a professional rather than trying to calculate it on your own.
4. Look for Refrigerant Leaks
Check around your unit for an oily substance, which could be a refrigerant liquid leak, and listen carefully for hissing sounds of refrigerant gas escaping. If you notice either of these signs, don’t attempt to fix the leak yourself. Refrigerant is a toxic substance, so call a professional HVAC technician to handle the job.
5. Clean the Condenser Coils
You can find condenser coils on the outdoor unit. They look like metal fins. Ensure the power to the unit is off before gently cleaning the coils of any dirt and debris using a soft brush.
How to Prevent Short Cycling
Prevention is better than repairs. A reliable maintenance plan and an experienced, professional team will ensure your system completes full cycles. Here are some tips for how to keep your AC running efficiently:
- Clean or replace air filters every three months, or monthly if you have pets.
- Inspect your units’ condenser coils monthly — being outside, they can quickly build up debris and dirt.
- Check around your vents and your refrigerant lines, which connect your inside and outside units, for frost or oily residue.
- Perform an annual thermostat calibration to confirm it’s working as it should.
When in doubt, always contact a professional. You may do more damage by mistake when trying to fix short cycling yourself, ending up with a more expensive repair. You can do rough calculations regarding AC sizing based on square footage and AC capacity in British thermal units (BTUs). However, double-checking your calculations with a professional who will also do the installation is best.
When to Call a Professional
If you’re experiencing short cycling and cleaning the filters and condenser coils doesn’t work, you should call a professional. They have the knowledge and equipment to deal with complex electrical issues, refrigerant leaks and handling, and will do an in-depth service or replacement of all major components.
At Thielmann Heating, Cooling, & Plumbing, we have been serving Southeast Wisconsin’s HVAC needs since 1929. Our expert technicians will give you a thorough maintenance tuneup service for your AC unit that you can opt for annually, seasonally or whenever you feel your AC isn’t as efficient as it should be.
Contact us today to schedule a service.
