E19 appears and the thermostat cannot control the heat pump; system may lock out.
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.
Possible Causes
How to Fix / Troubleshooting
Safety first: Turn off power to the heat pump and control circuits before working on wiring. Heat pumps contain high-voltage components.
- Check heat pump status: Look at the heat pump’s own display or LEDs for fault codes. Clear any lockouts according to the manufacturer’s instructions.
- Verify wiring: Confirm that the Delta Dore interface or relay contacts are wired to the correct heat pump terminals (call for heat, mode, etc.). Tighten all connections.
- Confirm configuration: In the installer menu, ensure the correct system type (heat pump) and control mode are selected.
- Reset interface: Power cycle the heat pump and the Delta Dore interface module, then test operation.
If E19 persists with correct wiring and configuration, the heat pump interface module or thermostat output may be faulty and should be checked by a professional.
Repair Difficulty
Required Part
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