High
Red neon on fascia on Glow-worm Fuelsaver Complheat 40 55

Your boiler has stopped working because the water pressure in the central heating system is too low.

Call an engineer soon

Book a Gas Safe engineer within 24 to 48 hours. Your boiler may be unsafe or could break down completely if left.

What the manual says

Manufacturer manual

Low water pressure. Fill central heating system, pressure 0.7bar min.

From this model's manual
Verified against the Glow Worm Fuelsaver Complheat 40 55 installation & service manual.
Plain-English guidance below. Severity, DIY steps, costs and parts are our interpretation to help you act, not text from the manual.

What causes this fault?

This fault occurs when the water level inside your central heating system drops too low for the boiler to operate safely. It is usually caused by a small leak in the pipework or radiators, or because the air cushion inside the expansion vessel has depleted over time.

This issue often surfaces in autumn when the heating is turned on for the first time after summer, as the change in temperature can highlight existing pressure drops.

Engineer required

This is a high severity fault. Stop using the boiler and call a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.

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