BoilerFaultCodesThe 6 most common faults
01
FAILED PELLET LIGHTING High DIY-safe
Your boiler has stopped working because it has completely run out of wood pellets.
What to try first
Check your bulk pellet store and hopper to confirm they are empty.Refill the pellet store with the correct grade of wood pellets.Follow the manufacturer's manual instructions to prime the feed system and reset the burner control panel.
02
SERVO MOTOR BLOCKED High Engineer
Your boiler has stopped working because the mechanical part responsible for feeding fuel into the fire is stuck, likely due to a build-up of ash residue.
Full guide for SERVO MOTOR BLOCKED03
PROBE FAULT High Engineer
Your boiler has lost the signal from one of its internal temperature sensors, which is preventing it from heating your home safely.
Full guide for PROBE FAULT04
AIR PRESSURE ERROR High Engineer
Your boiler is struggling to clear exhaust gases or draw in fresh air, so it has safely shut down to prevent unsafe operation.
Full guide for AIR PRESSURE ERROR05
41 High Engineer
Your boiler is struggling to get the wood pellets to catch fire, so it is currently pausing its startup process.
Full guide for 4106
29 High Engineer
Your boiler is struggling to clear exhaust gases effectively because the internal fan or air sensors are not working as they should, causing the system to stop for safety reasons.
Full guide for 29on the Grant Spira
Igniter elementFeed auger motorPellet feed motorBurner grateTemperature sensorWiring harness
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 Grant 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