Gledhill GB35C Fault codes & diagnostics

2 fault codes with plain-English explanations, severity ratings, DIY guidance, and repair cost estimates.

Combi Natural Gas 35 kW 2006 onwards Discontinued
GC Number 47-317-01
Download the Gledhill GB35C manual The official installation & service manual (PDF) — the exact document these fault codes were verified against. PDF

This boiler uses LED flash patterns

Count the flashes in one repeating group before the pause. That number is your fault code. Do not reset until you have noted it. How to read fault codes →

Versions & GC numbers

Which version do you have?

The GC number on your boiler's data badge identifies the exact appliance and production years, as recorded in the UK Product Characteristics Database.

GC number Appliance (register name) Produced
47-317-01 GB35C AGB5035 2006–present

Appliance names and production years are taken from the UK Product Characteristics Database (the SAP/SEDBUK register). Where a GC number is also printed in this model's own manufacturer manual, both sources were checked to agree.

Fault codes

All 2 documented codes

Tap any card for details

Flashing dot D2

Your boiler has detected a general ignition or operational failure and has locked itself out for safety.

High DIY-safe £100-280

What to check first

  1. Locate the 'set/reset' button (labelled S1) on the control panel.
  2. Press and release the S1 button to clear the fault.
  3. Observe if the boiler fires up and the flashing dot disappears.

Parts commonly replaced

  • Ignition Electrode
  • Gas Valve
  • PC B Control Board

Related codes

Full explanation for Flashing dot D2
FLASHING P

Your boiler has detected that the water pressure is too low, causing it to stop running to protect the system.

High DIY-safe £0-120

What to check first

  1. Locate the filling loop (usually a silver flexible hose) underneath the boiler.
  2. Slowly open the tap or taps on the filling loop to let water into the system.
  3. Watch the pressure gauge and close the taps once the needle reaches between 1 and 1.5 bar.

Parts commonly replaced

  • Filling loop
  • Pressure sensor
  • Expansion vessel

Related codes

Full explanation for FLASHING P
Status & diagnostic codes

1 operating states & engineer diagnostics

Not faults — these are normal operating states. Tap to expand.

FLASHING F Status Your boiler has detected very cold temperatures and has automatically turned on its high-level frost protection mode to prevent the internal pipes from freezing.