Common problems guide

The most common Potterton Envoy Plus problems

The faults most likely to send a Potterton Envoy Plus into lockout — with plain-English causes, what to check first, estimated repair costs and whether you need a Gas Safe engineer.

This model is discontinued. Parts can be harder to source and expensive. If repair costs are mounting, a new A-rated boiler may be the smarter choice.
19 documented codes
6 most common
1 DIY-safe checks
5 engineer needed

The 6 most common faults

01
Display not illuminated High DIY-safe

Your boiler has lost all power and is completely switched off, meaning you currently have no heating or hot water.

What to try first

Check that the main boiler on/off switch is in the 'on' position.Look at your home's fuse box or consumer unit to ensure the circuit breaker for the heating system hasn't tripped.Verify that the fused spur connection unit (usually a white switch with a fuse) near the boiler is switched on and that the fuse itself has not blown.

Est. cost
£100-250
Parts
PCB (Printed Circuit Board), External fuse or fused spur, Transformer
Full guide for Display not illuminated
02
Hot Surface Igniter High Engineer

Your boiler is failing to light the internal burner because the component responsible for creating the initial spark or heat has stopped working.

Est. cost
£150-250
Parts
Hot surface igniter, Ignition control board
Full guide for Hot Surface Igniter
03
Lockout High Engineer

Your boiler has detected a safety fault and has stopped working to prevent further issues, meaning you currently have no heating or hot water.

Est. cost
£150-350
Parts
Ignition electrode, Gas valve, Printed Circuit Board (PCB)
Full guide for Lockout
04
Pulse Red (1 flash) High Engineer

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

Est. cost
£120-220
Parts
NTC Thermistor, Temperature Sensor
Full guide for Pulse Red (1 flash)
05
Pulse Red (2 flashes) High Engineer

Your boiler has detected that it is getting too hot and has safely shut itself down to prevent damage.

Est. cost
£120-250
Parts
Case temperature sensor, NTC thermistor, Overheat thermostat
Full guide for Pulse Red (2 flashes)
06
Pulse Red (4 flashes) High Engineer

Your boiler is trying to start up but is unable to ignite its flame, so it has safely shut down to prevent gas from building up.

Est. cost
£120-250
Parts
Ignition electrode, Gas valve, PCB
Full guide for Pulse Red (4 flashes)
Parts most often replaced

on the Potterton Envoy Plus

PCB (Printed Circuit Board)External fuse or fused spurTransformerHot surface igniterIgnition control boardIgnition electrode

Based on parts cited in our fault code database. Your engineer will confirm what's actually needed after diagnosis.

Call a Gas Safe engineer if…

  • You can smell gas or see signs of a leak
  • The Potterton shows an Emergency or High severity code
  • The boiler keeps locking out after repeated resets
  • You've tried the DIY checks and the fault hasn't cleared
  • There's visible water leaking from the boiler
  • The flame is yellow or orange instead of blue
See the full 19-code list for the Potterton Envoy Plus

Related guides

Boiler losing pressure → No hot water → When to replace → Symptom checker →