You can fix this
Likely cause: a clogged air filter
A clogged filter traps heat inside the furnace, so its safety controls shut it off early. Replace the filter and watch the next few cycles.
Why this happens
Carrier, Bryant and Trane all list a dirty filter or restricted airflow among the causes of short cycling. When air can't move through, the furnace overheats and a limit switch shuts the burners off, then it cools and starts again. Bryant recommends checking the filter monthly and replacing it every 30 to 90 days.
How to fix it
- Set the thermostat to Off before you pull the filter.
- Replace the filter with the same size, arrow pointing toward the furnace.
- Set the thermostat back to Heat and time the next few cycles.
- Write the date on the new filter's edge and check it monthly, as Bryant suggests.
When to stop. Bryant says it's not recommended to leave a short cycling furnace running. If cycles are still under 7 minutes with a clean filter, turn the heat off and call an HVAC technician.
If this does not fix it, tell the HVAC technician
- How dirty the filter was and when it was last changed.
- How long cycles lasted before and after the new filter.
- Whether any vents were closed.
Build the full list: what to tell the HVAC technician.
Start this troubleshooter over
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