Lux
No Cooling Call from Thermostat
Thermostat will not start cooling even though it is set to COOL and the setpoint is below 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 Y wire at Lux wall plate, Misconfigured system type (heat-only), Open contactor coil in outdoor unit
How to Fix / Troubleshooting
Safety: Turn off power to both indoor and outdoor units before wiring checks.
- Verify mode: Confirm the thermostat is in COOL mode and not in HEAT or OFF.
- Inspect Y wiring: Remove the thermostat and ensure the Y wire is properly inserted and tightened in the Y terminal.
- System configuration: In the installer menu, verify that cooling is enabled and that the system is set to conventional A/C or heat pump as appropriate.
- Bypass test (advanced): With power on and thermostat removed, briefly jumper R to Y at the wall plate. If the outdoor unit starts, the thermostat is not sending a cool call and may be defective or misconfigured. Remove the jumper immediately after test.
- Outdoor unit check: If jumpering R to Y does not start the condenser, an HVAC technician should inspect the contactor, capacitor, and control wiring.
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Repair Difficulty
Medium
3/5
Required Part
Y Cooling Call Thermostat Conductor
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