What does the Sime ALARM 03 fault code mean?

Your boiler has too much water inside it, causing the pressure to rise to an unsafe level.

How much does it cost to fix Sime error code ALARM 03?

Typical repair cost for the Sime ALARM 03 fault is £80-160 including labour.

Locate a radiator bleed valve and use a key to release water into a container until the pressure gauge on the boiler drops.

Manufacturer manual

High system pressure (above 2.8 bar) — drain via drain valve until 1.0–1.5 bar

From this model's manual

Verified against the Sime Murelle He System installation & service manual.

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

Boiler cover options

A cover plan would handle faults like ALARM 03: no call-out fees, no surprise bills.

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Six most common causes of dropping pressure.

Step-by-step using the filling loop.

7 signs repair isn't worth it anymore.