Indoor unit displays E9 and unit may not respond to thermostat or remote commands
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.
Possible Causes
How to Fix / Troubleshooting
Safety: Turn off power to the indoor unit at the breaker.
Steps:
- Power reset: Leave power off for at least 5 minutes to allow capacitors to discharge, then restore power and see if E9 clears.
- Check grounding: Verify the air handler is properly grounded and that neutral and ground connections are tight.
- Inspect board for damage: Remove the control board cover and look for burnt components, bulged capacitors, or insect damage.
- Surge protection: If E9 occurred after a storm or outage, consider installing a surge protector on the HVAC circuit.
Note: Persistent E9 almost always indicates a failed indoor control board. Replacement with the correct Comfortmaker/ICP board and configuration should be done by a qualified technician.
Repair Difficulty
Required Part
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