Potterton Envoy Fault codes & diagnostics

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

Regular Natural Gas 8.8-23.4 kW 1994-2001 Discontinued

Replaced by: Suprima

Download the Potterton Envoy manualThe official installation and service manual (PDF), the document these fault codes were read from. 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 →

Severity at a glance

Each cell = one fault code. Hover to identify.
1 Emergency 8 High
Just want the most common Potterton Envoy faults?
The top 6 problems in plain English — with causes, DIY checks and repair costs.
Fault codes

All 9 documented codes

Tap any card for details

LED / flash-pattern codes
F (Flashing)

Your boiler has stopped working completely and entered a safety lockout mode to prevent further issues.

High DIY-safe £100-350

What to check first

  1. Locate the reset button on the control panel
  2. Press and hold the reset button for several seconds
  3. Wait for the boiler to attempt to restart
  4. Check that your gas pre-payment meter (if applicable) has credit

Parts commonly replaced

  • Ignition Electrode
  • Gas Valve
  • Printed Circuit Board (PCB)
Full explanation for F (Flashing)
Flashing

Your boiler has detected a safety issue and has shut itself down completely to prevent any potential danger.

High Engineer only £150-350

Parts commonly replaced

  • Ignition electrode
  • Gas valve
  • Printed circuit board (PCB)
  • Flame sensor
Full explanation for Flashing
Pulse Red (1 flash)

Your boiler has stopped working because it can no longer accurately read the temperature of the water inside it.

High Engineer only £120-200

Parts commonly replaced

  • NTC Thermistor
  • Temperature Sensor
Full explanation for Pulse Red (1 flash)
Pulse Red (3 flashes)

Your boiler has detected that it is dangerously overheating and has automatically shut itself down to prevent internal damage.

Emergency Engineer only £180-350

Parts commonly replaced

  • Overheat Thermostat
  • NTC Sensor
  • Pump
  • PCB
Full explanation for Pulse Red (3 flashes)
Pulse Red (4 flashes)

Your boiler is failing to ignite the flame needed to produce heat and hot water.

High Engineer only £120-250

Parts commonly replaced

  • Ignition lead
  • Ignition electrode
  • Gas valve
  • PCB
Full explanation for Pulse Red (4 flashes)
Pulse Red (5 flashes)

Your boiler has stopped because it cannot maintain a flame to heat your water, which means your heating and hot water have turned off.

High Engineer only £150-300

Parts commonly replaced

  • Ignition electrode
  • Gas valve
  • Flame rectification probe
  • PCB
Full explanation for Pulse Red (5 flashes)
Pulse Red (6 flashes)

Your boiler is failing to detect the internal airflow needed to ignite safely, so it has shut itself down to prevent a hazard.

High Engineer only £120-250

Parts commonly replaced

  • Air Pressure Switch
  • Flue fan
  • Venting tubes
Full explanation for Pulse Red (6 flashes)
Digital codes
Display not illuminated

Your boiler has no power going to it at all, meaning the screen is blank and it won't respond to any commands.

High DIY-safe £80-280

What to check first

  1. Check if your main electrical consumer unit has tripped
  2. Ensure the fused spur switch next to the boiler is turned on
  3. Check the 3-amp fuse inside the boiler's wall switch

Parts commonly replaced

  • Main Printed Circuit Board (PCB)
  • Internal Fuse
  • Transformer
Full explanation for Display not illuminated