How much does it cost to fix Potterton error code Lights: On Flash On?

Typical repair cost for the Potterton Lights: On Flash On fault is £120-200 including labour.

Lights: On Flash On High

Potterton Lights: On Flash On Fault Code

Q: What does the Potterton Lights: On Flash On fault code mean?

Your boiler has stopped working because it is unable to accurately measure its own internal temperature to control the heating process safely.

Also written as LIGHTSONFLASHON — same fault.

The Potterton Lights: On Flash On fault code means: your boiler has stopped working because it is unable to accurately measure its own internal temperature to control the heating process safely.. It appears on 3 Potterton models in our database.

Technical description: Thermistor fault. Go to Thermistor section of the fault finding instructions.

Typical repair cost £120-200 (including labour)

Engineer required

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

Find a Gas Safe engineer

Search the official register for a qualified engineer in your area.

Gas Safe Register →

Potterton models that show the Lights: On Flash On fault code

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

Source

Potterton Lights: On Flash On fault code information on this page is sourced and cross-checked against the official Potterton service / installation manuals for each affected model.

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