SEr Low

Vaillant SEr Fault Code

Also written as SER — same fault.

The Vaillant SEr fault code means: your boiler is simply reminding you that it is time for its scheduled annual safety check and service.. It appears on 1 Vaillant model in our database.

Monitor it

This is a minor fault. Keep an eye on it and mention it at your next annual boiler service. Reset the boiler and see if it clears.

Technical description: Maintenance indicator: service signal shown alternately with the current pressure after expiry of the set number of burner operating hours.
Typical repair cost £90-140 (including labour)

Engineer required

This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.

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Vaillant models that show the SEr fault code

Click a model for the full fault code list and model-specific repair notes.

Source

Vaillant SEr fault code information on this page is sourced and cross-checked against the official Vaillant service / installation manuals for each affected model.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 27 April 2026