Lennox Overheating Thermostat Electronics

Thermostat emits a burning smell or becomes unusually hot to the touch.

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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

Shorted internal component in Lennox thermostat, Incorrect voltage applied (e.g., 120V miswired to thermostat), Thermostat installed on hot surface or above heat source, Internal regulator failure

How to Fix / Troubleshooting

Safety warning: Immediately turn off power to the HVAC system at the breaker if you smell burning or feel excessive heat. Do not continue using the thermostat.

  • 1. De-energize system:
    • Turn off the furnace/air handler breaker and any dedicated thermostat power source.
  • 2. Remove thermostat:
    • Carefully remove the thermostat from the wall and inspect for scorch marks or melted plastic.
  • 3. Inspect wiring:
    • Verify only low-voltage (24V) wires are connected; never connect line voltage to a Lennox smart thermostat.
  • 4. Replace thermostat:
    • Do not reuse an overheated thermostat; install a new Lennox thermostat after correcting any wiring errors.
  • 5. Have wiring inspected:
    • Engage a qualified technician to ensure no damage occurred to the control board or wiring.
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Repair Difficulty

Hard 4/5

Required Part

Lennox Smart Thermostat
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