E9
Day & Night
Indoor Unit EEPROM Configuration / Addressing Error
E9 error, unit may not respond to thermostat commands or may run unexpectedly
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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
Incorrect DIP switch or jumper settings on indoor PCB, Corrupted configuration data, Replacement board not properly programmed for Day & Night model, Loose configuration module
How to Fix / Troubleshooting
Safety first: Disconnect power to the indoor unit before adjusting any switches or jumpers.
- Step 1 – Locate configuration switches: On the indoor control board, find the DIP switches or jumpers used to set airflow, tonnage, and system type. Refer to the unit's wiring diagram on the blower door.
- Step 2 – Verify settings: Compare current switch positions to the chart for your specific Day & Night model number. Correct any mismatched settings.
- Step 3 – Reseat configuration module: Some boards use a plug-in configuration or memory module. Gently remove and reinsert this module to ensure good contact.
- Step 4 – Power cycle: Restore power and allow the system to boot. Check if E9 clears and the unit responds normally.
- Professional help: If a replacement board was recently installed, it may require OEM programming or the correct configuration chip from Day & Night. This should be handled by an authorized technician.
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Repair Difficulty
Hard
4/5
Required Part
Indoor Control Board (Configured for Specific Model)
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