Potterton Kingfisher MF RSL/CFL Fault codes & diagnostics

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

Regular Natural GasLPG 12-30 kW 2001-2007 Discontinued
GC Number 41-590-36

Replaced by: Promax SL

Download the Potterton Kingfisher MF RSL/CFL manual The official installation & service manual (PDF) — the exact document these fault codes were verified against. PDF

The fault code is already on your display

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

Fault codes

All 2 documented codes

Tap any card for details

Red LED illuminated

Your boiler has automatically shut down for safety because it has become dangerously too hot, or because the flue is blocked and exhaust gases cannot escape properly.

Emergency Engineer only £120-250

Parts commonly replaced

  • Overheat Thermostat
  • Flue Thermostat
  • Flow Switch
  • Pump
Full explanation for Red LED illuminated
Red LED is 'ON'

Your boiler has detected an internal fault or is not receiving a signal to start, and has locked itself out for safety.

High DIY-safe £100-£350

What to check first

  1. Check that your room thermostat and programmer are turned up and calling for heat.
  2. Ensure the gas supply to the property is turned on.
  3. Turn the boiler temperature control knob to the 'Off' position, wait 10 seconds, then turn it back to your desired setting to attempt a reset.

Parts commonly replaced

  • Gas Valve
  • Ignition Lead
  • Printed Circuit Board (PCB)
  • External Thermostat
Full explanation for Red LED is 'ON'
Status & diagnostic codes

15 operating states & engineer diagnostics

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

CFL40 Diagnostic Your boiler has stopped working because it cannot sense that the pilot light has successfully ignited or is staying lit. CFL50 Diagnostic Your boiler is failing to light because it is not sensing the necessary air flow required for safe operation. CFL60 Diagnostic Your boiler has stopped working because it is not detecting the necessary airflow required to safely vent exhaust gases, causing the system to shut down to prevent unsafe operation. CFL70 Diagnostic Your boiler has stopped working because it is failing to sense that it is burning gas correctly, which means the system has shut itself down to keep your home safe. CFL80 Diagnostic Your boiler has detected an issue with the air supply or exhaust system, meaning it has shut down as a safety precaution to prevent dangerous gases from entering your home. CFL90 Diagnostic Your boiler has failed to ignite because the flue system is obstructed or not drawing air correctly, meaning it is currently unsafe to operate. CFL100 Diagnostic Your boiler has detected an issue with the air supply or exhaust system, meaning it is not venting fumes correctly and has safely shut down to prevent a hazard. Green 'Flame' led Status Your boiler is operating exactly as it should and is currently burning gas to heat your water or home. RSL40 Diagnostic Your boiler has stopped working because it has detected a failure in its internal safety control system, meaning it cannot safely ignite or heat your home. RSL50 Diagnostic Your boiler has stopped working because the internal thermostat has detected that the water temperature has risen too high, causing it to shut down for safety. RSL60 Diagnostic Your boiler has stopped working because the internal sensor has detected that the water temperature has risen too high, causing it to shut down for safety. RSL70 Diagnostic Your boiler has stopped working because the internal system is failing to detect that the burner has successfully lit, which is a common safety feature to prevent gas buildup. RSL80 Diagnostic Your boiler has stopped working because it is failing to detect a flame, which prevents it from safely heating your home. RSL90 Diagnostic Your boiler has stopped working because it has failed to ignite or stay lit, which is a common safety feature when the system detects a combustion or fuel supply issue. RSL100 Diagnostic Your boiler has stopped working because the safety sensors have detected an issue with the heat exchange or water flow, causing the unit to shut down to prevent damage.