Furnace locks out with E05; burner does not start and you may hear the fan running only.
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.
Possible Causes
How to Fix / Troubleshooting
Safety: Turn off power before removing covers. Do not operate the furnace with the flue system disassembled.
- Inspect flue and air intake: Go outside and check the concentric flue terminal for ice, leaves, nests, or other obstructions. Clear any blockage. Ensure the terminal is not submerged in snow.
- Check pressure hoses: Open the furnace and locate the air pressure switch and its silicone hoses to the fan or flue collector. Ensure hoses are firmly attached, not cracked, kinked, or filled with water. Drain any condensate and reattach.
- Test the pressure switch: With power off, gently blow through the hoses to ensure they are clear. Lightly tap the pressure switch body to free a stuck diaphragm.
- Reset and test: Restore power and call for heat. If E05 persists, the pressure switch or fan performance may be inadequate.
If you suspect a blocked internal flue path or a defective pressure switch, contact an authorized Kospel technician. Incorrect handling can lead to unsafe combustion and flue gas leakage.
Repair Difficulty
Required Part
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