E16
Gosund Aux/E Heat Output Fault

E16 error and thermostat cannot drive auxiliary/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

Failed AUX/E output relay, Miswired AUX/E terminal, Open circuit in AUX/E wire to air handler, Incorrect system configuration (aux heat disabled)

How to Fix / Troubleshooting

Danger: Turn off power to indoor and outdoor units before working on wiring.

  • Step 1 – Verify configuration:
    • In thermostat settings, ensure system type is set to Heat Pump with Aux/E Heat.
    • Confirm that auxiliary heat is enabled and configured correctly.
  • Step 2 – Inspect AUX/E wiring:
    • Check that the AUX/E wire is connected at both thermostat and air handler terminals.
    • Look for breaks or loose connections.
  • Step 3 – Test AUX/E circuit:
    • At the air handler board, jumper R to AUX/E to see if auxiliary heat engages.
    • If it does, but the thermostat cannot trigger it, the AUX/E output is suspect.
  • Step 4 – Measure AUX/E output:
    • With a call for emergency or auxiliary heat, measure voltage between AUX/E and C at the thermostat; should be ~24VAC.
    • If no voltage, the AUX/E driver is likely defective.
  • Step 5 – Replace thermostat if AUX/E driver is bad:
    • Replace the thermostat if E16 persists with known‑good wiring and air handler.
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Repair Difficulty

Hard 4/5

Required Part

Aux/E Heat Output Relay/Driver Circuit
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