Heat On Flashing
Honeywell Home
Burner Short‑Cycle Protection / Minimum Off Timer
Display shows 'Heat On' flashing and furnace does not start
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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
Built‑in heat call delay, Recent power interruption, Furnace lockout requiring reset, Thermostat configured with extended heat cycle delay
How to Fix / Troubleshooting
Safety: If you smell gas, leave the building and contact your gas supplier immediately.
- Allow delay to expire: Leave the thermostat in Heat mode with a higher setpoint than room temperature and wait 5 minutes.
- Check furnace power: Ensure the furnace switch is on and the breaker is not tripped.
- Reset furnace: Turn the furnace power switch off for 30 seconds and back on to clear a possible control board lockout.
- Inspect filter and vents: A severely clogged filter can cause overheating and lockout. Replace the filter and ensure supply/return vents are open.
- Call a professional: If 'Heat On' continues flashing and the furnace never starts, a limit switch, flame sensor, or control board issue may be present and should be serviced by a technician.
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Repair Difficulty
Medium
3/5
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