Heil
Short Cycling
Furnace short cycles: starts, runs briefly, then shuts off and restarts frequently.
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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 relative to duct system, Dirty flame sensor causing flame dropout, High limit opening due to restricted airflow, Thermostat anticipator or cycle rate set too aggressive
How to Fix / Troubleshooting
Safety: Turn off power before opening panels.
Steps to check:
- Replace filter: Install a clean filter and verify all supply and return registers are open.
- Thermostat settings: For mechanical thermostats, adjust the heat anticipator per the furnace control current rating. For digital thermostats, set a longer cycle rate (e.g., 3 cycles per hour instead of 6).
- Clean flame sensor: Remove and clean the flame sensor to prevent nuisance flame loss.
When to call a pro: If short cycling persists, a technician should check temperature rise, static pressure, and system sizing to determine if duct modifications or control changes are needed.
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Repair Difficulty
Medium
3/5
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