Thermostat shows E18 and reports an internal hardware fault; device may reboot repeatedly.

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

MCU self-test error, Internal bus communication failure between MCU and peripherals, Severe PCB damage from surge or moisture

Safety first: Turn OFF power at the breaker before removing the thermostat.

Steps to attempt:

Inspect for physical damage: Remove the thermostat and check the PCB for burn marks, corrosion, or signs of water ingress.
Dry the unit: If moisture is suspected, allow the thermostat to dry in a warm, dry location for 24 hours (power disconnected), then reinstall and test.
Power cycle: Restore power and observe if E18 returns immediately.

Persistent E18 indicates an internal hardware failure that is not field-repairable. Replace the thermostat.

Medium 3/5

Main Control Board Assembly

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