High Lockout
J3E on Ideal HP290

Your heat pump has stopped working because the internal computer responsible for powering the compressor has detected a technical fault.

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

Inverter Error

What causes this fault?

This fault occurs when the electronic controller that manages the compressor's power supply experiences a technical failure or internal short circuit. It is often caused by electrical surges, moisture ingress, or component degradation that prevents the unit from regulating the speed of the pump effectively.

This fault is more common during the peak of summer or winter when the system is under high load, causing the internal electronic components to run hotter for longer periods.

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

J5EView →H2View →

Related guides you might find useful

Banging / kettling / whistling noise

Each noise points to a different fault.

Read →

Boiler won't turn on — 9-step checklist

Work through these before the call-out.

Read →

Boiler keeps cutting out

Lockout fault with a reset-needed pattern.

Read →