E18
iComfort
Dehumidification Control Fault
Thermostat shows E18 and reports dehumidification sensor or control error
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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
Failed dehumidification sensor input, Miswired dehumidification terminal to wrong equipment input, Shorted dehumidification relay, Incorrect dehumidification configuration
How to Fix / Troubleshooting
Safety first: Turn off power to the HVAC system and any whole‑home dehumidifier before working on wiring.
- Step 1 – Review configuration: In the installer setup, verify that dehumidification is enabled only if a compatible dehumidifier or over‑cooling strategy is installed.
- Step 2 – Inspect wiring: Check the dehumidification control wires at the thermostat, interface module, and dehumidifier. Ensure they are on the correct terminals and not shorted.
- Step 3 – Test dehumidifier separately: If a standalone dehumidifier is used, test it by manually energizing its control terminals per the manufacturer’s instructions to confirm it operates.
- Step 4 – Disable feature for testing: Temporarily disable dehumidification in the thermostat settings. If E18 clears, the issue is likely with the external dehumidifier or its wiring.
- Step 5 – Replace thermostat/interface: If E18 persists with dehumidification disabled and wiring removed, the dehumidification control circuit on the thermostat or interface module may be defective and require replacement.
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Repair Difficulty
Medium
3/5
Required Part
iComfort Thermostat or Interface Dehumidification Output
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