High Lockout
F.92 on Vaillant ecoTEC Plus 625

Your boiler's internal computer is receiving the wrong information about its own identity, preventing it from running safely.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed

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

Coding resistor fault

What causes this fault?

This fault occurs when the boiler's main control board cannot verify which specific model it is installed in, usually due to a loose or faulty identification chip. The most common reason is a hardware failure in the small coding resistor or a communication breakdown on the main circuit board itself.

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.

Find a Gas Safe engineer
Search the official register →

Related fault codes

F.70View →

Related guides you might find useful

Boiler keeps cutting out

Lockout fault with a reset-needed pattern.

Read →

Yellow or orange flame — CO safety

Safety-critical — turn off, read this.

Read →

When to replace your boiler

7 signs repair isn't worth it anymore.

Read →