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efloresAug 14, 2025
Why is my Aprilaire 8840 Thermostat display blank?
- AAndrea PerezAug 14, 2025
If the display on your Aprilaire Thermostat is blank, here are a few things you can check: * Ensure the circuit breaker is on and reset it if needed. * Verify the power switch at the heating and cooling system is turned on. * Confirm that the furnace door is closed securely. * Inspect the wiring at the terminal block to ensure the reversing valve is correctly connected, with 'O' active for cooling and 'B' for heating.