Lux No Heat Call from Thermostat

Thermostat has power but will not turn on heat when temperature is set higher than room temperature

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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

Loose W/W1 wire at Lux wall plate, Misconfigured system type (set to cool-only), Open heating relay on furnace board

How to Fix / Troubleshooting

Safety: Turn off HVAC power at the breaker before touching wiring.

  • Verify mode: Ensure the Lux thermostat is set to HEAT mode and not OFF or COOL.
  • Check setpoint: Raise the set temperature at least 3–5°F above the displayed room temperature.
  • Inspect W/W1 wiring: Remove the thermostat and confirm the W or W1 wire is securely clamped in the correct terminal and not broken.
  • System configuration: In the installer menu, confirm the system type is set to conventional heat or heat pump as appropriate, and that heating stages are enabled.
  • Bypass test (advanced): With power on and thermostat removed, briefly jumper R to W at the wall plate. If the furnace starts, the thermostat is not sending a heat call and may be defective or misconfigured. Remove the jumper immediately after test.
  • Call technician: If jumpering R to W does not start heat, the issue is in the furnace or control board and requires HVAC service.
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Repair Difficulty

Medium 3/5

Required Part

W/W1 Heat Call Thermostat Conductor
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