High Lockout
E135 on Baxi Duo-tec Combi

Your boiler's internal computer has encountered a software glitch or a communication error that is preventing it from running properly.

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

Internal error

What causes this fault?

This fault occurs when the boiler's main control board experiences a software crash or fails to communicate with the internal sensors correctly. It is often caused by a sudden electrical surge, loose internal wiring, or a critical hardware failure within the printed 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.

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Related fault codes

E128View →E133View →E160View →

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