BoilerFaultCodesThe 5 most common faults
01
Red High Engineer
Your boiler has stopped circulating water because the internal pump has jammed, meaning you currently have no heating or hot water.
Full guide for Red02
Flashes red High Engineer
Your boiler has stopped heating because the internal water pump, which moves hot water around your house, has seized up or failed and cannot restart itself.
Full guide for Flashes red03
Constant Red High Engineer
Your Grant boiler has stopped because the water circulation pump is either jammed or has suffered an electrical failure, meaning your home will not get any heating or hot water.
Full guide for Constant Red04
Flashes red/green High Engineer
Your boiler is struggling because the internal water pump is stuck or not receiving power, which prevents heat from circulating through your home.
Full guide for Flashes red/green05
LED off High Engineer
Your boiler has completely lost power and is unable to turn on, meaning it cannot provide any heating or hot water.
Full guide for LED offon the Grant Vortex Pro 15-26
Central heating pumpPump headAutomatic air ventCirculator pumpPump capacitorWiring 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
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