Thermostat shows humidity but does not control dehumidification or humidification as configured

Warning: Turn off power before changing accessory wiring.

• Step 1 – Verify humidity settings:
  • In thermostat settings, ensure Humidify or Dehumidify control is enabled.
  • Set reasonable humidity setpoints (e.g., 45–50%).
• Step 2 – Check accessory wiring:
  • Confirm the humidifier/dehumidifier is wired to the correct accessory terminals.
  • Verify whether the accessory expects 24VAC or dry contact control and match the thermostat configuration.
• Step 3 – Test accessory manually:
  • Jumper the accessory’s control terminals to ensure it operates.
• Step 4 – Monitor operation:
  • Allow time for humidity to reach setpoint; humidity changes slowly compared to temperature.
• Step 5 – Replace thermostat if accessory output is nonfunctional:
  • If wiring and accessory are good but the thermostat never energizes the accessory output, the driver circuit may be faulty; replace the thermostat.