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5 Reasons an AC May Start Short-Cycling


An air conditioning system runs in cycles where the compressor turns on to provide cooling for the house, then shuts down until the thermostat registers it needs to turn back on. These cooling cycles should last at least fifteen minutes.

If you notice your AC shuts down after only a short time, then turns on again soon after, it’s short-cycling. This malfunction makes it hard for the air conditioner to fully cool a house. It also wastes energy (compressor start-up draws on large amounts of electricity) and wears down the AC components rapidly. Below we’ve listed five frequent causes of this problem.

1. A clogged air filter

Few small troubles can cause more big troubles than leaving an HVAC system air filter in place for too long. Once this filter becomes clogged, which can take from one to three months, it triggers a range of malfunctions in the air conditioner. A clogged filter can cause short-cycling because the restriction on airflow will lead to the AC overheating and shutting down early. You can prevent this by keeping up with regular filter changes.

2. Frozen evaporator coil

Several issues with an air conditioner can cause the evaporator coil to freeze, such as dirt along the coil’s surface or setting the thermostat too low. The ice on the coil throws off the AC’s standard cycling and can cause it to short-cycle. Don’t try to solve this problem by scraping off the ice, since this may damage the coil. You can shut off the AC to let the ice melt, but you’ll want professionals to investigate the cause of the frozen coil.  

3. Problems with the electrical system

Electrical malfunctions in the control board cause a majority of air conditioning system issues. Any fault in the control board can lead to the AC turning on and off at the wrong times.

4. The refrigerant level is low

The refrigerant level in an air conditioning system (known as the AC’s charge) should remain the same for the system’s lifetime. Leaks can lead to the charge dropping, and this will force the air conditioner to short-cycle—as well as numerous other problems leading eventually to a complete system breakdown.

5. The AC is too large

If this is a new air conditioner spending its first summer cooling your house, short-cycling may mean the system was not sized correctly for the space it must cool. Amateur installers commonly make the error of installing an air conditioner that’s too large for a house, which will cause the AC to cool the home so fast that it registers prematurely it’s completed a cooling cycle and shuts down. Repairs won’t solve this problem: the air conditioner must be replaced with a correctly sized one.

You’ll need professional HVAC service in Fresno, CA to solve most of these short-cycling problems (with the exception of changing the air filter). Our experts will diagnose the cause of your short-cycling air conditioner and provide the solutions necessary to keep your house cool.

Leave your AC repair needs to Purl’s Sheet Metal & Air Conditioning. “Quality Is the Cornerstone of Our Success” since 1952.

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