E9
ATAG
Lockout Due to Repeated Ignition Failure
Furnace locks out with E9, often after several failed ignition attempts
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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
Persistent ignition fault, Faulty gas valve, Incorrect gas/air ratio, Defective control board ignition circuit
How to Fix / Troubleshooting
Safety first: Do not repeatedly reset a furnace that fails to ignite; unburned gas can accumulate. Isolate gas and power before inspection.
- Follow the same checks as for ignition failure (electrodes, burner cleanliness, gas supply).
- Verify that the gas isolation valve to the appliance is fully open.
- Check for any smell of gas around the appliance; if detected, ventilate the area and call a gas emergency service immediately.
- After basic visual checks, restore power and perform a single reset. Observe whether the unit attempts ignition (fan, spark, gas valve click).
- If E9 reappears, do not continue resetting. A qualified ATAG technician must test the gas valve, combustion, and control board.
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Repair Difficulty
Professional Required
5/5
Required Part
ATAG main control PCB
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