Mains ON Only High

Potterton Mains ON Only Fault Code

Also written as MAINSONONLY — same fault.

The Potterton Mains ON Only fault code means: your boiler has detected an internal fault that has caused it to stop heating your home and hot water for safety reasons.. It appears on 1 Potterton model in our database.

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: Green LED: OFF, Red LED: ON
Typical repair cost £150-300 (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 →
Boiler cover options

Avoid the next call-out bill

A cover plan would handle faults like Mains ON Only: no call-out fees, no surprise bills.

Approved partner
Domestic Appliance Guard
Unlimited call-outs, 24/7 helpline, no price-hike promise
Get a quote →

Affiliate links. We may earn a commission at no extra cost to you.

Potterton models that show the Mains ON Only fault code

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

Source

Potterton Mains ON Only 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 7 July 2026