High Lockout
E37 on Vokera Pinnacle

Your boiler has identified a communication problem with the sensor that monitors water returning from your radiators, preventing the system from operating correctly.

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

Open circuit on return sensor

What causes this fault?

This fault occurs when the boiler's main control board loses its connection with the sensor that measures the temperature of water returning from the radiators. The most common reason is that the internal components of the sensor have failed, or the electrical wiring connecting it to the brain of the boiler has become loose or damaged.

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

E33View →E38View →

Related guides you might find useful

Boiler keeps cutting out

Lockout fault with a reset-needed pattern.

Read →

Radiators cold at the bottom

Sludge build-up — needs flushing, not bleeding.

Read →

Yellow or orange flame — CO safety

Safety-critical — turn off, read this.

Read →