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Boiler Error Codes for Bosch Models Explained

Posted on by Rudkin & Herbert Team

Modern boilers are the most reliable and efficient they have ever been and Worcester Bosch models are some of the best on the market. However, once in a while things can go wrong and this can leave the average homeowner scratching their head, not knowing what the problem is.

Your boiler will have a display panel and, should something go awry, it is here that an error code will show which gives insight into the source of the issue. To help you troubleshoot your boiler problems, we’ve put together a handy list of common boiler error codes for Worcester Bosch models.

Locking error

With locking errors, your boiler will show a flashing warning triangle and a fault code. At the same time, a static cause code will display. After clearing the fault, you will need to press the reset button.

Fault code Cause code Possible cause
9A 362 Incorrect heat control module (HCM) fitted
9U 233 Faulty or disconnected code plug
B7 257 Replacement control board needed
C6 215/216 Fan running too fast or too slow
C7 214/217 Fan not running or airflow blocked
D1 240 Sensor wet or damaged
D1 241 Sensor disconnected or damaged
D1 286 Boiler overheated
E2 222/223 Flow sensor shorted, damaged or disconnected
E5 218/332 Primary flow sensor overheated
E9 219 Main heat exchanger overheated – maximum temperature 105°C
E9 220 Maximum temperature sensor on main heat exchanger has failed
E9 221 Maximum temperature sensor on main heat exchanger not recognised
E9 224 Flue gas thermostat overheated
EA 227 Failure of four ignition attempts
EA 229 Loss of flame during operation
EA 234 Gas valve coil disconnected
EA 261 Flame not established during first four seconds of the ignition period
EA 338 Pump is not detecting water – check pressure gauge and repressurise to 1 bar


Blocking errors

With these errors, the boiler will stop operating without fault information automatically displayed. To see the codes, you need to press the spanner/return button. These errors will clear themselves after the associated fault is cleared.

Fault code Possible cause
A1 Little or no water in system – check pressure gauge and repressurise to 1 bar
C1 Fan has stopped
EA No flame is detected – the boiler will block during four ignition attempts and then turn into a locking fault
EF Boiler operating at minimum burner load with a temperature difference greater than 18°C between flow and return
No code Air lock or reduced water – check pressure gauge and repressurise to 1 bar
260 Sensor disconnected or no water – check pressure gauge and repressurise to 1 bar

Some of these common problems have easy fixes that you can carry out yourself – check out our blog post covering some of these solutions. If you need some help, an expert engineer from Rudkin & Herbert will be able to offer you quick and reliable assistance for maintenance and repair work. As a well-established business with a strong reputation throughout Leicestershire, you can always depend on our helpful team for high quality workmanship. Don’t hesitate to get in touch with any enquiries.