Answer
Mar 04, 2026 - 11:54 AM
An E1 error usually indicates a communication fault between the thermostat and your rooftop AC control board. It does not always mean the thermostat itself has failed. Common causes are a loose communication cable, a loss of 12V power to the control board, or a failed AC control board. If the error remains after resetting and verifying wiring connections, the issue may be with the rooftop AC control board rather than the thermostat.
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