F5 displayed, unit may not respond to remote or wall control properly

Safety: Turn off power to the indoor unit before removing the front panel.

• Access display board: Remove the front cover of the Fraser‑Johnston indoor unit to expose the display/keypad PCB.
• Check ribbon cable: Carefully disconnect and reconnect the ribbon cable or harness between the display board and main control board. Ensure it is fully seated and not kinked.
• Inspect for damage: Look for moisture, corrosion, or burn marks on the display board. If present, replacement is recommended.
• Test operation: Restore power and test buttons and display. If F5 remains, replace the display/keypad board with the correct Fraser‑Johnston part.