Short Cycling In Air Conditioners: Is The Thermostat To Blame?

Posted on: 23 August 2022


Short cycling is a common problem that affects different types of air conditioners and can be caused by a number of underlying problems. 

What Is Short Cycling?

When an air conditioning system is functioning properly, it will keep blowing cool air into your home until the ambient temperature reaches the temperature you have set your thermostat to. When an air conditioner starts short cycling, it cuts out just a few seconds or minutes after it activates.

Because the air conditioner does not run long enough to adequately cool your home, it will reactivate itself a short time later, only to deactivate itself again before the desired temperature is reached. This seriously diminishes the cooling power of your air conditioner, and massively increases its energy consumption. If it is not fixed swiftly, a short cycling air conditioner can cause your energy bills to skyrocket.

How Do Faulty Thermostats Cause Short Cycling?

Thermostats can suffer from a number of faults that cause air conditioners to short cycle. Here are some potential thermostat-related causes of short cycling:

Damaged Wiring

Your air conditioner's thermostat is attached to the main body of the air conditioner via signaling wires, which transmit the activation and deactivation signals that turn your air conditioner on and off. If this wiring is damaged or frays, the signals sent by the thermostat can be distorted, causing short cycling.

If your thermostat is wall-mounted, its wiring may have been damaged by recent remodeling or redecorating work. Water damage caused by leaks and flooding can also seriously damage thermostat wiring. If your thermostat has been in use for many years, its wiring may have failed due to simple wear and tear.

Faulty Anticipator

If your air conditioning system uses a mechanical thermostat, it will almost certainly contain an anticipator. This small device acts as a time delay for the thermostat's activation signals and prevents the thermostat from activating the air conditioner the moment ambient temperatures get slightly warmer or colder than the desired setting.

A properly functioning anticipator prevents short cycling, but it can also cause short cycling if it is damaged or poorly adjusted. 

Thermostat Is Not Level

Some older thermostats contain mercury bulb temperature sensors, which keep a constant measure of the ambient temperature around the thermostat. Mercury bulb sensors must be kept level to function properly. If the thermostat is knocked or twisted off-kilter, the mercury bulb may not be able to measure temperatures accurately, causing short cycling.

What Should You Do If A Faulty Thermostat Is Causing Short Cycling?

If your air conditioning system is short cycling, and you have ruled out common causes that you can fix yourself (such as dirty air filters), you should call in a professional air conditioning repair service to inspect your thermostat. Other problems that aren't related to the thermostat can also induce short cycling, so it is generally a good idea to have the entire system inspected for faults and malfunctions.

If your repair service finds problems with the thermostat that are causing short cycling, the thermostat can be repaired or replaced quickly and simply. If your system uses a mechanical or mercury bulb thermostat, it may be a good idea to pay a little extra and have the thermostat replaced with a modern, digital model, since digital thermostats are generally more reliable.