Thermostat displays E9 and touchscreen is unresponsive or erratic

Safety first: Turn off power to the HVAC system at the breaker before removing the thermostat.

• Step 1 – Power cycle: Remove the thermostat from the wall plate for 60 seconds, then reinstall. Check if the touchscreen responds.
• Step 2 – Clean screen: Wipe the screen with a soft, dry cloth to remove oils or debris that may interfere with touch detection. Do not use harsh chemicals.
• Step 3 – Inspect for damage: Look for cracks, chips, or signs of impact on the glass. Physical damage usually requires replacement.
• Step 4 – Check internal connection: If you are comfortable with electronics and the thermostat design allows, gently open the housing and verify that the display ribbon cable is fully seated on the main board. Only do this with power off.
• Step 5 – Firmware reset: If the touchscreen is intermittently responsive, navigate to Settings > System > Factory Reset (if accessible) to reload default configuration. Note that this will erase custom settings.
• Step 6 – Replace display module: Persistent E9 or a dead touchscreen indicates a failed display/digitizer assembly. Replace the thermostat or display module as specified by iComfort.