Worcester Bosch Boiler Fault & Error Codes

Has a fault developed on your Worcester Bosch Boiler? If your boiler has an issue then it will enter a safe lock-out mode and provide an error code. 

In order to help you determine what this error code could mean we have generated descriptions for each of them below. If you are still unable to fix the issue then please don't hesitate to get in contact with one of our expert boiler engineer partners who can help fix your heating troubles.

General Faults & Errors

This section is an overview of all of the types of errors that can occur on a Worcester Bosch boiler.

IssueDescription
Blocking ErrorsIf this occurs then there will be no fault data displayed and the boiler will cease operating. You can find the cause of this in the info menu which is accessed by pressing the spanner or return button on your boiler. When the fault clears the condition will clear automatically, such as if you wait for an area to cool. It can be found that in some cases a blocking error has a time duration before it changes to a locking condition.
Cause ErrorA cause error is a three digit number which is displayed, however during a blocking error it won't appear, although you can still access the information from the menu.
Fault ErrorThis is an alpha numeric code that indicates the fault group.
Locking ErrorWhen there is a locking error the boiler flashes with a warning triangle and a fault code at the same time. The cause code will be displayed and in order to clear the fault you will need to manually press the reset button on the boiler fascia.
Maintenance CodesThese are codes that are displayed with the letter H which is then followed by a number. The code advises the situation but will not stop your boiler from working. Maintenance code list below.

Locking Errors

Here is a list of the fault codes that occur for a Worcester Bosch locking error, most of these are fixed by the reset button with the exception of B7.

Fault CodesCause CodesDescriptionPotential Cause
9A362Heat Control Module (HCM)HCM fitted incorrectly
9U233Heat Control Module (HCM)Faulty or not connected code plug
B7257Internal errorReplace control board
C6215Fan issueThe fan is running too fast
C6216Fan issueThe fan is running too slow
C7214Fan issueThe fan is not running
C7217After a defined period of time there is no airflowThe fan is not running or the airflow has been blocked
D1240Error for return sensorSensor wet or damaged (the boiler will block for 300 seconds before this condition)
D1241Error for return sensorSensor disconnected or damaged (the boiler will block for 300 seconds before this condition)
D1286The temperature of return is too highOverheating boiler
E2222Short circuit flow sensorDamaged or flow sensor disconnected
E2223Open circuit flow sensorDisconnected or damaged flow sensor
E5218Flow temperature too highPrimary flow sensor overheat
E5332110C temperature limit has been exceeded on the primary flow sensorPrimary flow sensor overheat
E9219Temperature too high on safety sensorThere is a maximum temperature of 105C, this means that the heat exchanger has exceeded this.
E9220Short circuited safety sensorMaximum temperature sensor on the main heat exchanger has failed
E9221Open circuit on the safety sensorMaximum temperature sensor on the main heat exchanger has not been recognised
E9224The max temperature thermostat has been activatedOverheated flue gas thermostat
EA227After the ignition no flame has been detectedThis error occurs after the failure of four ignition attempts. There is a 30 second wait between each attempt.
EA229During operation there has been a loss of flame signalThe established flame has been extinguished which could be caused by moisture in the stump or a strong wind into the flue
EA234Error in the gas valveGas valve coil disconnected
EA261Timing error on ignitionDuring the first 4 seconds of the ignition period a flame was not established
EA338Too many short burner starts without confirmationThe pump is not detecting water, you need to check the pressure gauge and repressurise to 1 bar

Blocking Errors

If this occurs then there will be no fault data displayed and the boiler will cease operating. You can find a list of the block errors for Worcester Bosch boilers in the table below:

Fault CodesCause CodesDescriptionPotential Cause
A1281Running in air or the pump could be stuckCheck the pressure gauge and re pressurise to 1 bar as there is little or no water in the system
C1264During operation the airflow has stoppedThe fan has stopped working
EA227After ignition no ionisation has been detectedThe boiler blocks at 4 attempts of ignition before going to locking fault. No flame is detected.
EF349Central heating, boil detect.
Large delta T despite minimum burner.
There is a greater than 18C Return & Flow temperature difference so the boiler is operating at minimum burner load
N/A212Flow temperature has risen too fastCheck the pressure gauge and re pressurise to 1 bar as there is an air lock or reduced water content
N/A213The difference in temperature between the supply and return exceeds the limit Check the pressure gauge and re pressurise to 1 bar as there is an air lock or reduced water content
N/A260No temperature rise after burner startsCheck the pressure gauge and re pressurise to 1 bar as the sensor has disconnected or there is no water content