Worcester Bosch boiler faults

Worcester bosch boiler control panel

Should a fault develop with your Worcester Bosch boiler, it will enter a safety lock-out mode, and fault code information will be generated as described below.

Worcester Bosch fault codes: locking errors

When a locking error occurs, the boiler display will flash a warning triangle and fault code. If you see the following fault codes on your Worcester Bosch boiler, the fault will need to be fixed (using our helpful guide below) and the boiler reset the boiler using the button on the control panel.

Some fixes will need to be completed by a Gas Safe registered engineer. 

9A: HCM (Heat control module)

9U: HCM (Heat control module)

B7: Internal error

C6: Fan problem

Cause code: 215

Cause code: 216

Cause code: 214

Cause code: 217

D1: Return sensor error

Cause code: 240

Cause code: 241

D1: Return temperature too high

E2: Flow sensor short circuit

Cause code: 223

E5: Flow temperature too high

E5: Primary flow sensor has exceeded 110°C

E9: Safety sensor temperature too high

E9: Safety sensor short circuit

E9: Safety sensor open circuit

Cause code: 221
Possible cause: Maximum temperature sensor on the main heat exchanger has not been recognised

E9: Max temperature thermostat activated

EA: No flame detected after ignition

EA: Loss of flame signal during operation

EA: Gas valve error

EA: Ignition timing error

EA: Too many short burner starts without confirmation

Worcester Bosch fault codes: blocking errors

With a blocking error, the boiler will stop operating and won’t display a fault code. You can still access the cause code in the info menu by pressing the spanner/return button, which should give you a better idea of what’s going on.

The condition will clear automatically when the associated fault clears e.g. waiting for an area to cool. In some cases, a blocking error has a defined time duration prior to changing to a locking condition.

A1: Pump stuck or running in air

C1: Airflow stopped during operation

EA: No ionisation detected after ignition

EF: Central heating, boil detect – Large delta T despite minimum burner

No code: Safety or flow temperature rises too fast

No code: Temperature difference between supply and return exceeding limit

No code: No temperature rise after burner starts

Maintenance codes

These are displayed with the letter H followed by a number. The code advises of a situation that will need some attention but is not a fault that will stop the boiler from functioning. Some of the common ones are listed:

H11

Hot water outlet sensor defect. Hot water can still be delivered but with less control.

H13

This can mean that your boiler is due for a service. It shows when an internal timer expires in the boiler to remind you about your annual boiler service. You can also disable this reminder by finding the appropriate settings in your boiler manual.

Boiler repairs from HomeServe

Experiencing problems with your Worcester Bosch boiler? Our expert repairs team are on hand to diagnose the issue and will aim to get things working again in no time.

Alternatively, if you’re looking for a new boiler, we’re working together with BOXT, one of the largest boiler installation companies in the UK, to help you find the best boiler for your home.

BOXT makes choosing the perfect new boiler for your home easy with a fixed price quote on your screen in just 90 seconds.

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