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.
22 documented codes
6 most common
5 DIY-safe checks
1 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
E09 High DIY-safe

Your boiler has detected that the water pressure is too low, causing the system to shut down for safety.

What to try first

Locate the filling loop (a flexible silver hose) underneath the boiler.Slowly open the one or two taps on the loop until you hear water entering the system.Watch the pressure gauge and close the taps once the needle reaches between 1 and 1.5 bar.

Est. cost
£0-160
Parts
Filling loop, Expansion vessel, Pressure sensor
Full guide for E09
03
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
04
E01 High DIY-safe

Your boiler has failed to light the gas or cannot confirm a flame is present, meaning it cannot provide heat or hot water.

What to try first

Check if your gas supply is active by testing another gas appliance like a hob.Verify that your credit meter has sufficient funds.Press the Reset button on the boiler control panel for 3 seconds.

Est. cost
£120-350
Parts
Ignition electrode, Gas valve, Printed Circuit Board (PCB)
Full guide for E01
05
E03 High DIY-safe

Your boiler has detected that it has become too hot and has shut down as a safety precaution to prevent damage.

What to try first

Check that all radiator valves are fully open to allow water to flow.Ensure your system water pressure is between 1.0 and 1.5 bar on the pressure gauge.Press the reset button on the control panel to see if the fault clears after the system has cooled down.

Est. cost
£100-250
Parts
Overheat Thermostat, Circulation Pump, Main Heat Exchanger (if blocked)
Full guide for E03
06
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
Parts most often replaced

on the Heatline Solaris

Filling loopExpansion vesselPressure relief valvePressure sensorIgnition electrodeGas valve

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 22-code list for the Heatline Solaris

Related guides

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