A14
Sime
Control Board Communication Fault
Furnace shows a communication error between the main control board and user interface or remote controller.
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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 low‑voltage communication cable, Faulty room thermostat or controller, Defective display board, Main PCB failure
How to Fix / Troubleshooting
Safety first: Turn off power before handling control wiring.
- Check controller connections: Inspect the wiring between the Sime furnace and any external room thermostat or digital controller. Tighten terminal screws and ensure polarity is correct.
- Inspect display board: Remove the front panel and check the ribbon cable between the display/user interface and the main PCB. Reseat both ends carefully.
- Test with simple thermostat: If possible, temporarily connect a basic on/off thermostat or link the call‑for‑heat terminals as per the Sime wiring diagram to see if the furnace responds.
- If communication remains faulty: Either the display board or main control board may be defective and should be diagnosed and replaced by a technician.
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Repair Difficulty
Medium
3/5
Required Part
Main Control Board / Display Board
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