Boiler shows E17; may indicate overcurrent or internal protection trip on power stage.

Safety first: Immediately isolate the boiler. Do not attempt repeated resets; serious electrical damage or fire could result.

• Inspect high-current wiring: With power off, check all element and supply terminals for signs of arcing, burning, or loose screws.
• Test elements for shorts: Using a multimeter, check resistance between each element terminal and between terminals and earth. Very low resistance or continuity to earth indicates a short.
• Check PCB power devices: Look for burnt triacs, relays, or tracks on the PCB. A strong burnt smell often indicates failure.
• Replace damaged components: Any shorted element or visibly damaged PCB must be replaced. Ensure all connections are tightened to the manufacturer's torque specifications.
• Professional testing: Due to the risk of further damage, final testing should be carried out by a qualified engineer with appropriate test equipment.