ALL 42 Medium

Sime ALL 42 Fault Code

Also written as ALL42 — same fault.

The Sime ALL 42 fault code means: your boiler's control panel is struggling to register your button presses because one of the buttons is stuck or the electronic interface is malfunctioning.. It appears on 3 Sime models in our database.

Book a service

This fault should be looked at by a Gas Safe engineer within the next week or two. It may get worse if left.

Technical description: Button fault
Typical repair cost £120-250 (including labour)

Engineer required

This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.

Find a Gas Safe engineer

Search the official register for a qualified engineer in your area.

Gas Safe Register →
Boiler cover options

Avoid the next call-out bill

A cover plan would handle faults like ALL 42: no call-out fees, no surprise bills.

Approved partner
Domestic Appliance Guard
Unlimited call-outs, 24/7 helpline, no price-hike promise
Get a quote →

Affiliate links. We may earn a commission at no extra cost to you.

Sime models that show the ALL 42 fault code

Click a model for the full fault code list and model-specific repair notes.

Source

Sime ALL 42 fault code information on this page is sourced and cross-checked against the official Sime service / installation manuals for each affected model.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 7 July 2026