E6
Keystone
Communication Error Between Display Board and Main Control Board
Keystone air conditioner displays E6 and may not respond to remote or panel commands properly.
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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 display-to-main board harness, damaged communication cable, oxidized connectors, failed display PCB or main PCB
How to Fix / Troubleshooting
Safety: Unplug the unit before removing any control panel or front cover.
Steps:
- Access control panel: Remove the front bezel to expose the user interface (display) board and its wiring harness.
- Check connectors: Locate the multi-pin cable between the display board and the main control board. Unplug and replug both ends several times to clean contacts. Ensure the locking tabs engage.
- Inspect cable: Look for pinched, cut, or burnt sections of the harness. Replace the harness if any conductor appears damaged.
- Visual board check: Examine both PCBs for burnt components, corrosion, or cracked solder joints around the connector area.
- Component swap (if available): If you have access to a known-good display board or main board (e.g., from an identical donor unit), swap one at a time to identify the faulty board.
- Replace defective board: Install a Keystone-compatible display PCB or main control PCB as needed, matching the model number and revision.
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Repair Difficulty
Hard
4/5
Required Part
Main Control Board or Display Control Board
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