E19
Wiser
Cooling Output / Reversing Valve Control Fault
Thermostat shows E19 and cannot control cooling (for heat pump / cooling-enabled systems)
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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
Miswired cooling relay on Heat Hub, Faulty reversing valve coil, Incorrect system type configuration, Failed cooling relay on hub PCB
How to Fix / Troubleshooting
Safety first: Cooling and heat pump controls are mains or high-voltage. Isolate power before opening any covers.
- Check system configuration: In the Wiser app, ensure the system is set to the correct type (heat pump, cooling enabled) and that cooling outputs are assigned correctly.
- Inspect wiring (qualified persons only): Verify that the cooling call and reversing valve terminals on the Heat Hub are wired to the correct inputs on the heat pump or air handler.
- Test coil resistance: With power off, measure the reversing valve coil resistance and compare with manufacturer specs. Replace if open or shorted.
- Bypass test (engineer only): A heating engineer may temporarily energise the cooling relay manually to confirm the external equipment responds.
- If E19 persists with correct wiring and good coil: Replace the Heat Hub as the cooling relay or driver is likely faulty.
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Repair Difficulty
Professional Required
5/5
Required Part
Wiser Heat Hub cooling / reversing valve relay
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