Potterton Kingfisher MF 40-100 Fault codes & diagnostics

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

Regular Natural Gas 11.7-29.3 kW 2001-2007 Discontinued
GC Number 41-393-95

Replaced by: Promax SL

Choose your boiler type

The Kingfisher MF 40-100 range comes in 13 types

Pick the one you have. The fault codes, GC numbers and manual differ by type.

RS40 0 codes · 1 GC number RS60 0 codes · 1 GC number RS70 0 codes · 1 GC number RS80 0 codes · 1 GC number RS90 0 codes · 1 GC number RS100 0 codes · 1 GC number CF40 0 codes · 1 GC number CF50 0 codes · 1 GC number CF60 0 codes · 1 GC number CF70 0 codes · 1 GC number CF80 0 codes · 1 GC number CF90 0 codes · 1 GC number CF100 0 codes · 1 GC number
Each model has its own manual A family spans several manuals, one per model or generation. Pick your model above and its page has the manual its fault codes were read from.

The fault code is already on your display

Note it down before pressing reset — resetting clears the code immediately. How to read fault codes →

Just want the most common Potterton Kingfisher MF 40-100 faults?
The top 6 problems in plain English — with causes, DIY checks and repair costs.
Fault codes

All 4 documented codes

Tap any card for details

Flue blockage

Your boiler has detected that waste gases are not escaping correctly through the flue, so it has safely shut itself down to prevent harmful fumes from entering your home.

Emergency Engineer only £120-250 Shared across the Kingfisher Mf range

Parts commonly replaced

  • Flue Terminal
  • TTB Sensor
  • Flue seals
Full explanation for Flue blockage
Overheat condition

Your boiler has switched itself off for safety because it detected that it has become too hot to operate safely.

High Engineer only £120-250 Shared across the Kingfisher Mf range

Parts commonly replaced

  • Overheat thermostat
  • Pump
  • PCB
Full explanation for Overheat condition
Red LED

Your boiler has become too hot and has automatically switched itself off as a safety precaution.

High Engineer only £120-250 Shared across the Kingfisher Mf range

Parts commonly replaced

  • Overheat thermostat
  • Pump
  • PCB
Full explanation for Red LED
Red LED (TTB)

Your boiler has sensed a problem with the dangerous exhaust gases escaping, so it has automatically shut itself down to keep your home safe.

Emergency Engineer only £120-250 Shared across the Kingfisher Mf range

Parts commonly replaced

  • Flue Thermostat
  • Flue Terminal
  • Fan
Full explanation for Red LED (TTB)