You can fix this
Likely cause: blocked or closed vents
Closed or covered vents trap heat in the furnace and ducts, which can trip its safety controls. Open them up.
Why this happens
Trane lists restricted airflow among the causes of short cycling. When registers or return grilles are closed or covered, warm air backs up and the furnace overheats and shuts off early. Carrier's advice is to rule out airflow problems first, and if that doesn't fix it, shut the system off and call a professional.
How to fix it
- Open every supply vent, including in rooms you don't use.
- Move furniture, rugs and drapes off vents and return grilles.
- Set the thermostat to Heat and time the next few cycles.
- If cycles stay short, turn the heat off and call an HVAC technician.
When to stop. If the furnace still short cycles with open vents and a clean filter, turn it off. Bryant says it's not recommended to leave a short cycling furnace running.
If this does not fix it, tell the HVAC technician
- Which vents or returns were closed or blocked.
- How long cycles lasted before and after opening them.
- When the filter was last changed.
Build the full list: what to tell the HVAC technician.
Start this troubleshooter over
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