ac short cycling

AC Short Cycling: Causes & How to Fix It

Does your air conditioner start working just fine and then stop after a few seconds or minutes? This is called short cycling. 

While minor adjustments might be all that’s needed sometimes, in many cases, you will need to call an HVAC professional. All in all, the cause of short cycling must be sorted as soon as possible to avoid facing a premature AC replacement.

Understanding Short Cycling

The term short cycling refers to a situation where the air conditioner turns on and off frequently.

How is this strange?

A normal AC goes through three cooling cycles per hour. When your home is hot, the thermostat notices it and triggers the AC to turn on and cool your home. The compressor kicks in and causes the refrigerant to move through the unit and cool the warm air coming in.

This cycle takes approximately 10 minutes, after which the air in your home cools down to the set level, and the AC shuts down to rest for ten minutes.

Unfortunately, when there is a slight malfunction with the AC, the compressor can stop before the cooling cycle is complete, hence the name short cycling. If left unattended, the cycle will keep getting shorter and shorter until the AC can no longer cool your home.

Consequences of Air Conditioner Short Cycling

Again, short cycling is a symptom of a problem in the AC, but it can also cause other problems, including the following:

  • High electricity bill: The AC uses the most energy when the compressor turns on. When it’s short cycling, it seems to be constantly starting up, which can use quite a lot of power. This is the first sign homeowners notice when their AC starts to short cycle.
  • Warm house: The AC has one job: to cool your house when it’s hot. Unfortunately, short cycling means the unit is not completing the cooling cycle and therefore not cooling your home.
  •  Reduced AC lifespan: When the compressor has to start every few seconds, it wears down quite fast. A compressor is the most expensive AC component to replace, so much so that it makes more sense to replace the entire unit.

Causes of AC Short Cycling and How to Fix Them

There are five reasons why the AC could be short cycling. Identifying the exact culprit is the best way to stop this detrimental behavior and figure out how to fix a short cycling air conditioner.

1. Clogged Filter

It’s amazing how many AC issues you can avoid just by simply replacing the air filter regularly. The build-up of dust, pollen, and debris on the filter prevents airflow and causes other components, including the compressor, to work harder. When there is not adequate airflow, parts overheat, and the system has to shut down every few minutes to avoid overheating.

Solution

A simple replacement of the air filter will sort out the problem.

2. Oversized Air Conditioner

If your AC is new and you have already started to notice short cycling, the problem could be that it is too large. This is what happens. When you set your thermostat to, let’s say, 70°F and your house is 78°F, it takes approximately 10 minutes for your entire house to reach 70°F and then AC shuts off.

When the AC is too big, it blasts cold air too fast and tricks the thermostat to think the entire house has reached 70°F in just a few minutes. This not only leads to air conditioner short cycling but also an uneven distribution of cool air. As a result, the warm air in other parts of the house quickly warms the parts that are cooled, and the AC has to start again in a few seconds.

Solution

Ultimately, the solution to this is to replace the unit with a properly sized one.

3. Frozen Evaporator Coils

Evaporator coils are responsible for cooling the warm air. However, these coils can freeze because of issues such as a clogged filter, malfunctioning fan, and low refrigerant. Frozen coils cannot adequately cool down the air, and this causes the AC to overheat and shut down regularly.

Solution

The first step is to shut down the AC completely and let the coils thaw. However, you also have to determine the cause of the freezing so it doesn’t happen again.

4. Low Refrigerant

Refrigerant is what moves the heat from your house to the outside through the evaporator coils. Under normal conditions, an AC comes with enough refrigerant to last its entire lifespan. 

However, this changes if there is a leak and refrigerant levels go down. Without enough refrigerant, the AC can’t cool down the air, and this causes overheating and, consequently, short cycling.

Solution

The solution here would be to find the leak and seal it. The HVAC tech will also top up the refrigerant to the required amount and ensure it doesn’t leak anymore.

5. Thermostat and Electrical System issues

The thermostat controls the AC. If it’s wrongly placed or wrongly calibrated, it misreads your home’s temperature and signals your AC to turn on and off prematurely. Another issue could be the control board which is difficult to resolve.

Solution

If you suspect the problem could be electrical, the best approach is to call the air conditioner company and talk to an electrician there.

Other HVAC Short Cycling Solutions

If the AC unit is relatively old, the cause for short cycling may not be any of the above. With age comes the deterioration of components like the compressor, thermostat, and low-pressure control switch. 

A good HVAC technician will tell you if any of the components are worn out and need replacement. In the case of a worn-out compressor, it is better to buy a new AC, which will be more efficient.

When all is said and done, the best way to prevent AC short cycling is regular maintenance. Change the air filter monthly and have the components cleaned by a professional at least three times a year. 

You can also use a hosepipe or blower to blow the dirt off the evaporator coils, compressor and condenser before the scheduled maintenance date. Finally, have the refrigerant level tested to see if there is a leak.

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