TP-Link Kasa
Aux/E Heat Output or Configuration Error
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, Aux heat disabled in thermostat configuration, Miswired W/AUX terminal, Failed Aux relay on thermostat
How to Fix / Troubleshooting
Safety: Turn off power to indoor unit before wiring checks.
- Verify wiring: At thermostat and air handler, ensure the AUX/E or W2 wire is connected to the correct terminals.
- Configuration: In the Kasa app, confirm the system is set as a heat pump with auxiliary heat and that Aux/E is enabled.
- Test Aux mode: Set thermostat to Emergency Heat (if available) and raise setpoint. If heat does not come on, the issue is in wiring, thermostat Aux output, or air handler controls.
- Technician jumper test: A technician can jumper R to AUX/E at the air handler to verify auxiliary heat operation. If it works with a jumper but not via thermostat, replace the thermostat.
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Repair Difficulty
Hard
4/5
Required Part
Aux/E Heat Output Relay / Wiring
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