AC Short CyclingExplained

When a system starts, runs a few minutes, shuts off and starts again, it is called short cycling. This is worth noticing in a Las Vegas summer because the system has to run long cycles in weeks over 100°F. A system that keeps stopping early struggles to hold the set temperature.

What Causes Short Cycling

Short cycling can point to several different issues inside your cooling system. Some causes are simple airflow problems you can fix yourself, while others require a technician to diagnose the internal components. In many cases, the system shuts down early because a safety switch detects a problem and turns the unit off to prevent permanent damage.

A dirty air filter is one of the most common reasons for short cycling. When the filter gets clogged with dust from the July and August monsoon winds, the indoor blower motor cannot pull enough air over the evaporator coil. Without warm air flowing over it, the indoor coil becomes too cold and can freeze into a solid block of ice. The system then shuts down as a safety measure. Once the ice melts, the cycle starts over again.

Refrigerant Issues

Air conditioners use refrigerant to absorb heat from inside the house and release it outside. If your system is low on refrigerant, it means there is a leak somewhere in the copper lines or the coils. Low refrigerant causes a drop in pressure. This pressure drop triggers a low-pressure safety switch, which shuts the compressor down. After the system rests, the pressure equalizes and the unit tries to start again, resulting in an endless loop of short cooling cycles.

You cannot simply add more refrigerant to fix the problem. The technician must find the leak, repair it, and then weigh in the correct amount of refrigerant. Keep in mind that anyone who maintains, services or repairs equipment containing refrigerant must hold EPA Section 608 certification.

Oversized Equipment

Sometimes the problem is not a broken part, but the size of the equipment itself. An air conditioner must be sized correctly for the specific home it cools. If the system is too large for your house, it will drop the indoor temperature very rapidly. The thermostat detects the sudden temperature drop and turns the system off before it has a chance to run a full cycle.

The constant starting and stopping is hard on the equipment. When the time comes for a replacement, a proper in-home estimate looks at the whole home before recommending a size. This includes checking the insulation, the windows, the existing ductwork, and the sun exposure.

How to Prevent Short Cycles

You can prevent some of the most common airflow issues with basic maintenance.

• Check the filter every month and change it at least every three months.
• Keep the vents inside your home open and unblocked by furniture.
• Schedule a cooling tune-up in the spring to check the electrical connections.
• Make sure the outdoor unit is clear of bushes and yard debris.

When to Request Service

If you change the air filter and the unit continues to turn on and off rapidly, you should turn the system off at the thermostat. Running it this way can damage the compressor. A technician can test the capacitor, check the refrigerant pressures, and inspect the safety switches to find the cause.

Kestrel Heating & Air provides AC repair across the valley. Our technicians find the cause first, show you what failed, and give a written price with repair and replacement options before any work begins. You can also join the Kestrel Comfort Club to receive a cooling tune-up every spring and a heating tune-up every fall.