ALL 40 High

Sime ALL 40 Fault Code

Also written as ALL40 — same fault.

The Sime ALL 40 fault code means: your boiler has detected that the electricity supply coming from your home's mains is unstable or at the wrong frequency, preventing it from starting safely.. It appears on 3 Sime models in our database.

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.

Technical description: Incorrect supply frequency detected
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 40: 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 40 fault code

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

Source

Sime ALL 40 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