22 fault codes with plain-English explanations, severity ratings, DIY guidance, and repair cost estimates.
Replaced by: Promax SL
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 →
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 |
|---|---|---|
| 41-591-87 | Promax SL 15 | 2007–present |
| 41-591-88 | Promax SL 24 | 2007–present |
| 41-591-80 | Promax 18 HE Plus | 2006–2006 |
| 41-591-79 | Promax 12 HE Plus | 2006–2006 |
| 41-601-17 | Promax 24/2 HE Plus | 2005–2010 |
| 41-601-22 | Promax 30 HE Plus | 2005–2010 |
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Your boiler has stopped working because it cannot properly move the gases required for combustion to safely leave the system.
Your boiler is failing to start because it isn't receiving enough electricity from your home's power supply.
Your boiler has switched itself off because it has detected that its internal temperature has become dangerously high.
Your boiler's electronic control centre is experiencing a critical internal failure and can no longer safely operate the heating or hot water system.
Your boiler's internal computer has developed a fault and is failing to control the system, meaning the boiler cannot operate safely or reliably.
Your boiler has detected that there is not enough water inside the system to operate safely and has shut down to prevent damage.
Your boiler has stopped working because a sensor that measures water temperature is providing an incorrect reading or has failed, causing the system to shut down for safety.
Your boiler has detected that the electricity supply wires are connected the wrong way around, which prevents it from operating safely.
Your boiler’s internal computer has developed a fault and is failing to send the correct signals to start or maintain your heating and hot water.
Your boiler has stopped working because a sensor that measures the water temperature is either faulty or unable to provide a correct reading to the control system.
Your boiler has stopped working because it cannot detect that water is flowing through the system, so it is choosing not to fire to protect itself from damage.
Your boiler has switched itself off because it has detected an unsafe temperature level to prevent overheating.
Your boiler has detected an issue with the sensing system that monitors the internal combustion area, which prevents it from firing up to keep your home safe.
Your boiler has detected an internal issue with the main heating unit, which means it has safely shut itself down to prevent damage.
Your boiler has stopped working because the mechanical fan responsible for venting exhaust gases safely out of your home is not responding or has a loose connection.
Your boiler has failed to light the flame, which means it has safely shut itself down to prevent any gas build-up.
Your boiler has switched itself off for safety reasons because it cannot light its flame or has become too hot to operate.
Your boiler has failed to light the flame and has turned itself off for safety reasons.
Your boiler has lost its electrical connection to a key internal component and has automatically shut down to prevent damage.
Your boiler has detected that it is getting too hot and has automatically switched itself off to prevent damage or safety risks.
Your boiler has stopped working and needs a manual restart to try and clear a temporary internal error.
Your boiler is currently unable to read the water temperature correctly, so it has shut down to prevent overheating.
BoilerFaultCodes