Carrier
Thermostat or Sizing-Related Short Cycling
The furnace cycles on and off frequently (every few minutes), but the house never reaches the set temperature.
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Possible Causes
Thermostat located in a draft or near a heat source, incorrect thermostat anticipator or cycle rate setting, oversized furnace, dirty flame sensor causing intermittent flame loss
How to Fix / Troubleshooting
Safety first: Turn off power before removing thermostat covers or furnace panels.
- Check thermostat location: Ensure the thermostat is not near supply registers, exterior doors, or direct sunlight.
- Review thermostat settings: For programmable thermostats, adjust the cycle rate or heat anticipator (if available) according to the thermostat manual for gas furnaces.
- Clean flame sensor: If burners shut off after only a few seconds, clean the flame sensor as described earlier.
If the furnace is significantly oversized, duct modifications or equipment changes may be needed; consult an HVAC professional.
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Repair Difficulty
Easy
2/5
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