Common problems guide

The most common Johnson Starley C26d problems

The faults most likely to send a Johnson Starley C26d 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.
23 documented codes
6 most common
2 DIY-safe checks
4 engineer needed

The 6 most common faults

01
E01 High DIY-safe

Your boiler has tried to light several times but has been unable to create a flame, meaning you have no heating or hot water.

What to try first

Check if other gas appliances, like a hob, are working to ensure gas is being supplied to the property.Ensure your gas meter has credit if you use a pre-payment meter.Press and hold the reset button for five seconds to see if the boiler restarts.

Est. cost
£100-£350
Parts
Ignition Electrode, Gas Valve, PCB (Control Board)
Full guide for E01
02
E18 High DIY-safe

Your boiler has stopped working because the waste water produced during heating cannot drain away correctly, usually due to a blocked or faulty pump.

What to try first

Check the external white plastic drainage pipe for any signs of freezing or blockages.Ensure any flexible hoses connected to the condensate pump are not kinked or trapped.If the outlet pipe is frozen, gently pour warm (not boiling) water over the pipe to thaw it.

Est. cost
£120-220
Parts
Condensate pump, Float switch sensor, Condensate discharge pipework
Full guide for E18
03
E02 High Engineer

Your boiler thinks it sees a flame even though it hasn't actually started the ignition process yet.

Est. cost
£120-280
Parts
Flame sensing electrode, Ignition lead, Main PCB
Full guide for E02
04
E03 High Engineer

Your boiler has shut down because its internal temperature has gotten too high and a safety switch has tripped to prevent damage.

Est. cost
£120-£250
Parts
Overheat Thermostat, Circulation Pump, Thermistor
Full guide for E03
05
E04 High Engineer

Your boiler has stopped working because it cannot detect that the combustion fan is spinning properly to safely vent waste gases.

Est. cost
£180-450
Parts
Combustion Fan, Main PCB, Wiring Harness
Full guide for E04
06
E05 High Engineer

Your boiler's internal thermometer that measures incoming air temperature has developed a fault, meaning the system can't regulate its operation correctly.

Est. cost
£120-£210
Parts
Inlet air thermistor (NTC sensor), Wiring harness, Control PCB
Full guide for E05
Parts most often replaced

on the Johnson Starley C26d

Ignition ElectrodeGas ValvePCB (Control Board)Condensate pumpFloat switch sensorCondensate discharge pipework

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 Johnson Starley 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 23-code list for the Johnson Starley C26d

Related guides

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