Baxi Solo 3 Fault codes & diagnostics

4 fault codes with plain-English explanations, severity ratings, DIY guidance, and repair cost estimates.

Regular Natural Gas 9-41 kW 1997-2006 Discontinued

Replaced by: Solo HE

Download the Baxi Solo 3 manual The official installation & service manual (PDF) — the exact document these fault codes were verified against. PDF

This boiler uses LED flash patterns

Count the flashes in one repeating group before the pause. That number is your fault code. Do not reset until you have noted it. How to read fault codes →

Just want the most common Baxi Solo 3 faults?
The top 6 problems in plain English — with causes, DIY checks and repair costs.
Fault codes

All 4 documented codes

Tap any card for details

Lights Flash Flash On

Your boiler has stopped working because the internal fan, which safely clears waste gases, is unable to start or spin correctly.

High Engineer only £250-£450

Parts commonly replaced

  • Fan Assembly
  • Fan Wiring Harness
  • Main Control Board
Full explanation for Lights Flash Flash On
Lights Flash Off Flash

Your boiler is not receiving enough electrical power from the main supply to operate safely.

High DIY-safe £0-120

What to check first

  1. Check if other appliances in your home are flickering or behaving strangely
  2. Check your fuse box (consumer unit) for any tripped switches
  3. Contact your electricity provider to see if there is a known power fluctuations issue in your area

Parts commonly replaced

  • External fuse
  • Printed Circuit Board (PCB)
Full explanation for Lights Flash Off Flash
Lights Flash Off On

Your boiler has got too hot and has shut itself down for safety, which is why your heating and hot water have stopped working.

High DIY-safe £90-180

What to check first

  1. Turn the boiler power off at the wall socket or fused spur
  2. Allow the boiler to cool down for at least 30 minutes
  3. Press the 'Reset' button (located at the bottom of the boiler) or turn the control knob to the 'R' position and back to 'On'

Parts commonly replaced

  • Overheat Thermostat
  • Flow Thermostat
  • Circulation Pump
Full explanation for Lights Flash Off On
Lights On Off Flash

Your boiler has detected that the electrical wiring coming into the unit is connected backwards, which is a safety risk and prevents the system from starting.

Emergency Engineer only £80-150

Parts commonly replaced

  • None - wiring correction required
Full explanation for Lights On Off Flash
Status & diagnostic codes

6 operating states & engineer diagnostics

Not faults — these are normal operating states. Tap to expand.

30 Status The number 30 is not a fault code for your Baxi Solo 3, but rather indicates the boiler's power output rating of 30,000 Btu/h. 40 Status Your boiler has detected that it is not firing up correctly, usually because the pilot light has gone out or there is an issue with the ignition process. 50 Status Your Baxi Solo 3 boiler is not experiencing a fault code; rather, 50 is a capacity indicator confirming your boiler is the 50,000 Btu/h model version. 60 Status Your boiler has stopped working because it has detected a failure to ignite or maintain a flame. 70 Status The number 70 on your boiler is not a fault code, but a label indicating that your boiler is a 70,000 Btu/h model. 80 Status Your boiler has reached its maximum heat output capacity, meaning it is currently running at its highest intensity to meet the heating demand.