Common problems guide

The most common Heatline Solaris problems

The faults most likely to send a Heatline Solaris 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.
11 documented codes
6 most common
2 DIY-safe checks
4 engineer needed

The 6 most common faults

01
0.8bar High DIY-safe

Your boiler has detected that the water pressure is too low for it to operate safely and effectively.

What to try first

Locate the filling loop (usually a silver flexible hose) underneath the boiler.Slowly open the one or two taps/valves until you hear water entering the system.Watch the pressure gauge and close the taps once the needle reaches between 1.0 and 1.5 bar.

Est. cost
£0-120
Parts
Filling loop, Expansion vessel, Pressure relief valve
Full guide for 0.8bar
02
F0 High DIY-safe

Your boiler has stopped working because the water pressure inside the system is too low.

What to try first

Locate the flexible filling loop underneath the boiler.Slowly open the small valves on the loop until you hear water entering the system.Watch the pressure gauge and close the valves once the needle reaches between 1.0 and 1.5 bar.

Est. cost
£0-120
Parts
Filling loop, Pressure sensor, Expansion vessel
Full guide for F0
03
F9 High Engineer

Your boiler has detected that the internal air extraction fan is spinning when it should be switched off, which prevents the system from starting up safely.

Est. cost
£150-250
Parts
Fan assembly, Printed Circuit Board (PCB)
Full guide for F9
04
F1 High Engineer

Your boiler has automatically shut down for safety because its internal temperature has climbed too high.

Est. cost
£120-250
Parts
NTC sensor, Primary heat exchanger, Pump
Full guide for F1
05
F2 High Engineer

Your boiler is struggling to accurately detect the temperature of your hot water, which means it has stopped heating it up to prevent the system from getting too hot.

Est. cost
£120-220
Parts
DHW NTC sensor
Full guide for F2
06
F3 High Engineer

Your boiler has stopped working because it is unable to accurately measure the temperature of the water inside the system.

Est. cost
£120-220
Parts
NTC Temperature Sensor, Wiring harness
Full guide for F3
Parts most often replaced

on the Heatline Solaris

Filling loopExpansion vesselPressure relief valvePressure sensorFan assemblyPrinted Circuit Board (PCB)

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 Heatline 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 11-code list for the Heatline Solaris

Related guides

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