Thermia
Ignition or Flame Sustain Failure without Display Code
Furnace starts and then shuts down within a minute, with the blower running only briefly.
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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
Marginal flame sensor signal, Intermittent gas valve operation, Loose ground connection, Weak hot surface igniter on Thermia furnace
How to Fix / Troubleshooting
Safety first: Turn off power and gas before cleaning or tightening components.
- 1. Clean flame sensor: Remove and gently clean the Thermia flame sensor rod with fine steel wool. Reinstall in the flame path.
- 2. Tighten ground connections: Ensure the burner assembly and control board ground wires are secure and free of corrosion.
- 3. Observe flame: Watch through the sight glass to see if the flame is stable or flickers out before shutdown. Unstable flame requires professional combustion diagnosis.
- 4. Check wiring to gas valve: Inspect connectors for looseness or corrosion.
- 5. If problem persists: Have a technician test flame signal microamps and gas valve operation.
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Repair Difficulty
Hard
4/5
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