E13
Amazon Smart Thermostat
Aux/E Heat Output Fault
Thermostat displays E13 and auxiliary/emergency heat will not engage
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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
Open Aux/E wire, Loose connection at air handler heat strip relay, Failed Aux/E output on thermostat
How to Fix / Troubleshooting
Safety: Turn off power to the air handler and any electric heat strips at the breaker.
- Check Aux/E wiring: Confirm the Aux/E wire is connected to the Aux/E terminal on the thermostat wall plate and to the appropriate terminal on the air handler control board.
- Inspect heat strip relay: Look for loose spade connectors or burned contacts on the electric heat relay (if visible).
- Test emergency heat mode: From the thermostat or Alexa app, switch to Emergency Heat and see if the system responds. If not, suspect wiring or relay issues.
If wiring and relays are intact and E13 remains, the thermostat’s Aux/E output circuit may be faulty and the thermostat should be replaced.
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Repair Difficulty
Hard
4/5
Required Part
Amazon Smart Thermostat Main Control Assembly
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