Junkers Overtemperature at Heat Exchanger

E8 displayed; unit may shut down during operation, often at high output.

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

Blocked primary heat exchanger, Insufficient water flow, Faulty overheat sensor, Pump failure (on pumped models)

Safety: Allow the heater to cool fully before touching it.

Increase flow: Open hot taps more fully to increase flow through the heater.
Clean filters and aerators: Remove restrictions that reduce flow.
Check pump (if fitted): On models with an internal pump, listen for pump operation and feel for vibration. A silent, hot pump may be seized.
Arrange descaling: If the unit is older and in a hard water area, schedule professional descaling.

Hard 4/5

Primary Heat Exchanger / Overheat Sensor

Check Price on Amazon

We may earn a commission from links on this page.