20 Emergency

Gledhill 20 Fault Code

The Gledhill 20 fault code means: your boiler is struggling to turn off the flame as quickly as it should after a heating cycle, which is a safety concern that prevents it from restarting.. It appears on 1 Gledhill model in our database.

Act immediately

Turn off your boiler and stop using gas appliances. Call a Gas Safe engineer now. This fault can be dangerous if ignored.

Technical description: FLAME_OUT_TOO_LATE_ERROR
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 20: 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.

Gledhill models that show the 20 fault code

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

Source

Gledhill 20 fault code information on this page is sourced and cross-checked against the official Gledhill service / installation manuals for each affected model.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 7 July 2026