Symptoms
- AC runs for a few minutes then shuts off repeatedly
- House never quite reaches the set temperature
- Cycling seems faster than it used to be
Likely causes
- CommonDirty air filter restricting airflowPoor airflow can cause the coil to freeze intermittently, cutting cycles short.
- CommonThermostat placed near a draft, vent, or heat sourceA thermostat reading the wrong temperature can cycle the system incorrectly.
- PossibleLow refrigerantLow refrigerant can cause the coil to ice up and trip a safety shutoff repeatedly.
- PossibleOversized AC unit for the houseAn overly powerful unit cools the air quickly and shuts off before a full dehumidifying cycle completes.
- PossibleFailing capacitor causing the compressor to struggle on startupA weak capacitor can cause the compressor to trip a safety switch shortly after starting.
What to do
- Replace the air filter if it's dirty or overdue.
- Check the thermostat isn't near a sunny window, heat vent, or drafty door that could cause a false reading.
- Turn the system off for 30 minutes to let it fully reset, then observe a full cycle.
- Check the indoor coil for ice, which points toward airflow or refrigerant as the cause.
- If cycling is new and hasn't always been this frequent, suspect a developing refrigerant leak or failing capacitor.
- Call an HVAC technician if short cycling continues after filter and thermostat placement checks.
Tools and parts
AC air filterSearch: “central air filter size replacement”
When to call a pro
Call an HVAC technician if short cycling continues after basic checks; refrigerant level, sizing, or a failing capacitor may be the cause.
Safety
Generally low risk
Generally low risk for a careful person. Stop if anything looks different from what this guide describes.