Unknown
Neon A Flashing on and off on Alpha SY9 24

Alpha SY9 24 fault code Neon A Flashing on and off

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed

What the manual says

Manufacturer manual

Overheat thermostat has operated. Rotate selector switch to the reset position (3) to reset

From this model's manual
Verified against the Alpha/Alpha Sy9 24 installation & service manual.
Plain-English guidance below. Severity, DIY steps, costs and parts are our interpretation to help you act, not text from the manual.

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 →
Boiler cover options

Avoid the next call-out bill

A cover plan would handle faults like Neon A Flashing on and off: 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.

All 8 fault codes on the SY9 24

Seeing a different code? Every code this model can display, in one place.

Neon A and B Flashing on and off alternativelyNeon A and B Flashing on and off at the same timeNeon A Illuminated continuouslyNeon A Illuminated continuously and B flashingNeon B Flashing on and offNeon B Flashing very slowly (every 5 seconds)Neon B Illuminated continuously

Related guides you might find useful

Is boiler cover worth it?

Break-even maths on monthly cover.

Read →

When to replace your boiler

7 signs repair isn't worth it anymore.

Read →

New boiler cost 2026

Realistic UK prices for a swap.

Read →