Napoleon
Short Cycling Due to Overheating or Thermostat Issues
Furnace short cycles: starts, runs for a few minutes, 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
Dirty air filter, Closed or blocked supply registers, Oversized furnace for duct system, Thermostat located in poor location or with anticipator misadjusted
How to Fix / Troubleshooting
Safety first: Turn off power before removing panels.
- Replace filter: Install a new filter of the correct size and recommended MERV rating. Avoid overly restrictive filters that can reduce airflow.
- Open vents: Ensure at least 80–100% of supply registers are open. Do not close multiple registers to "force" air to certain rooms; this can cause overheating.
- Thermostat checks: Make sure the thermostat is not directly above a supply register or near exterior doors. If it is, consider relocating it.
- Observe limit operation: If the burners shut off and the blower continues to run for a while before restarting, the high limit may be opening due to overheating. This requires airflow and possibly ductwork evaluation by a technician.
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Repair Difficulty
Medium
3/5
Required Part
High Limit Switch
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