Glow-worm Domestic hot water temperature sensor fault (on DHW-equipped Glow-worm furnaces/boilers)

F8 displayed, furnace locks out during operation, may be associated with hot water demand on combi-style furnace/boiler units

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

Failed DHW NTC sensor, Scale build-up around sensor pocket, Loose or corroded sensor connector, Wiring harness fault to Glow-worm PCB

Safety: Isolate power and water supply before removing any DHW components. Hot water can cause scalding.

Technician steps:

Locate the DHW NTC sensor on the plate heat exchanger or DHW outlet pipe.
Disconnect and measure sensor resistance; compare with Glow-worm temperature/resistance chart.
Inspect for limescale build-up around the sensor pocket; descale if necessary.
Check wiring continuity back to the PCB.
Replace the DHW NTC sensor if readings are incorrect or intermittent.

Medium 3/5

DHW Temperature NTC Sensor

Check Price on Amazon

We may earn a commission from links on this page.