F11
Ideal
Low-Voltage / Communication Fault
Furnace displays F11, blower may run continuously, no heating output
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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
Loose harness between user interface and Ideal control board, shorted low-voltage wiring, incorrect polarity or grounding, failed communication module on PCB
How to Fix / Troubleshooting
Safety: Isolate power before removing covers. Avoid pulling on wires; use connectors.
Steps:
- Check door switch: Ensure the blower door is properly fitted and engaging the safety switch; some Ideal furnaces will fault if the door is not secure.
- Inspect harnesses: Locate the communication cable between the display/interface (if fitted) and the main control board. Reseat both ends firmly.
- Look for damaged cables: Trace low-voltage cables for signs of rubbing, pinching, or rodent damage. Repair or replace as needed.
- Polarity check (for qualified persons): Confirm live, neutral, and earth are correctly wired at the furnace supply. Incorrect polarity can cause control issues.
- If F11 persists: The communication circuit on the control board may be defective and will require professional replacement.
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Repair Difficulty
Hard
4/5
Required Part
Main Control Board
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