E5
Certikin
Thermostat / Setpoint Control Fault
E5 error on display; heater may not respond to thermostat changes.
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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
Faulty internal thermostat circuit on Certikin PCB, Stuck relay controlling burner demand, Incorrect wiring of external thermostat, Shorted thermostat sensor
How to Fix / Troubleshooting
Safety first: Isolate power before accessing the control board or thermostat wiring.
- Check setpoint: Verify that the desired temperature is set correctly and that any external thermostat is calling for heat.
- Inspect external controls: If an external thermostat or BMS is connected, check its wiring and operation.
- Listen for relays: When calling for heat, listen for relay clicks on the PCB. No sound may indicate a failed relay or control circuit.
- Power cycle: Turn the heater off for several minutes, then back on to clear any temporary logic fault.
If E5 remains, the control PCB or thermostat circuit likely needs professional diagnosis and replacement.
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Repair Difficulty
Hard
4/5
Required Part
Certikin thermostat / main control PCB
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