9 fault codes with plain-English explanations, severity ratings, DIY guidance, and repair cost estimates.
The fault code is already on your display
Note it down before pressing reset — resetting clears the code immediately. How to read fault codes →
The GC number on your boiler's data badge identifies the exact appliance and production years, as recorded in the UK Product Characteristics Database.
| GC number | Appliance (register name) | Produced |
|---|---|---|
| 41-592-42 | Promax 12 System ErP | 2008–present |
| 41-592-43 | Promax 15 System ErP | 2008–present |
| 41-592-44 | Promax 18 System ErP | 2008–present |
| 41-592-45 | Promax 24 System ErP | 2008–present |
| 41-592-46 | Promax 32 System ErP | 2008–present |
Tap any card for details
Your boiler has lost its ability to measure the temperature of the water circulating through your radiators, causing the system to shut down for safety.
Your boiler has detected a problem with how it disposes of waste gases or condensation, causing it to shut down for safety.
Your boiler has switched itself off because it has detected that the water inside has become too hot.
Your boiler has detected that the water pressure is too low for it to operate safely and has shut down as a precaution.
Your boiler is struggling to move water correctly through the system, which is causing it to shut down to prevent overheating.
Your boiler has shut down because a sensor has detected that the exhaust gases are getting too hot, which is a safety measure to prevent damage.
Your boiler has failed to light because either gas is not reaching the burner or the flame is not being detected.
Your boiler's fan, which safely clears exhaust fumes from the unit, is not spinning at the correct speed or has lost electrical communication.
Your boiler has sensed that water is not circulating properly before the burner ignites, often due to trapped air or a blockage.
BoilerFaultCodes