High Lockout
F.65 on Vaillant ecoTEC Pro 28

Your boiler's internal control board has overheated or suffered an electrical failure, causing the system to shut down to prevent damage.

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

Fault: Electronics temp. - Electronics defective or too hot due to external influences

What causes this fault?

This fault occurs when the boiler's main control board reaches an unsafe temperature or suffers an internal electrical short circuit. The most common reason is a physical failure of the electronic components on the circuit board, though it can occasionally be caused by heat soak from other failing parts within the boiler casing.

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

F.61View →F.62View →F.67View →

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