Lennox
Standalone Dehumidifier Control Failure
Thermostat fails to control whole-home dehumidifier connected as a separate unit to Lennox system.
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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
Incorrect dehumidifier control wiring to thermostat dehumid terminals, Misconfigured dehumidifier type in thermostat, Failed relay in dehumidifier, Open or shorted low-voltage control cable
How to Fix / Troubleshooting
Safety warning: Turn off power to both the indoor unit and dehumidifier before adjusting wiring.
- 1. Confirm wiring diagram:
- Follow Lennox and dehumidifier manufacturer diagrams for control wiring.
- 2. Verify thermostat settings:
- Ensure the thermostat is set to control an external dehumidifier and humidity setpoint is below current humidity.
- 3. Test dehumidifier independently:
- A technician can jumper the dehumidifier control terminals to verify it runs.
- 4. Replace thermostat or repair wiring if control signal is not being sent:
- If the dehumidifier works when jumpered but not from thermostat, suspect thermostat output or wiring.
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Repair Difficulty
Medium
3/5
Required Part
Lennox Smart Thermostat
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