Lux
Aux/E Heat Control Failure
Thermostat fails to control auxiliary or emergency heat on a heat pump 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
Aux/E wire not connected to W2/E terminal, Heat pump configuration incorrect in installer menu, Open aux heat relay on air handler
How to Fix / Troubleshooting
Safety: Turn off power to the air handler/heat pump before wiring checks.
- Verify wiring: At the Lux wall plate, ensure the Aux/E conductor is connected to the W2 or E terminal as specified by the Lux manual.
- Installer configuration: In the installer menu, set system type to heat pump with auxiliary heat and enable Aux/E outputs.
- Test emergency heat: Switch the thermostat to EM HEAT mode and raise the setpoint. If no heat is produced, the issue may be in the air handler's aux heat relay or elements.
- Call technician: Have an HVAC technician inspect the aux heat strips, relays, and safeties if wiring and configuration are correct.
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Repair Difficulty
Hard
4/5
Required Part
Aux/E Heat Thermostat Conductor
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