Miller
Short Cycling Due to Control or Sizing Issues
Furnace cycles on and off rapidly (every few minutes) without reaching set temperature.
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Safety Warning
This repair may involve working with high voltage components or water connections. Always unplug the appliance before removing any panels.
If you are not confident in your ability to perform this repair safely, we strongly recommend contacting a professional technician.
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Possible Causes
Oversized furnace, Thermostat located near heat source, Dirty flame sensor causing flame drop-out, High limit cycling
How to Fix / Troubleshooting
Safety: Turn off power before accessing internal components.
- Check thermostat location: Ensure the thermostat is not near supply registers, direct sunlight, or other heat sources. Relocate if necessary.
- Clean flame sensor and check limits: Clean the flame sensor and verify the high limit is not tripping due to airflow issues (check filter and ducts).
- Adjust thermostat settings: Some thermostats allow adjustment of cycle rate or differential. Set to a longer cycle if available.
- Professional evaluation: If the furnace is significantly oversized, consult an HVAC professional about options such as duct modifications or equipment replacement.
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Repair Difficulty
Medium
3/5
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