BoilerFaultCodesWorcester Bosch A7 Fault Code
The Worcester Bosch A7 fault code means: your boiler is struggling to accurately measure the temperature of your hot water, which usually means your taps will only run cold or slightly warm.. It appears on 40 Worcester Bosch models in our database.
Technical description: Hot water NTC sensor defective.
What causes the Worcester Bosch A7 fault?
This fault occurs when the internal sensor responsible for monitoring the temperature of your hot water fails to send a reliable signal to the main control board. The most common reason is natural wear and tear or corrosion on the sensor's probe, which prevents it from reading how hot the water is, causing the boiler to shut down the burner for safety. In some cases, it can also be triggered by a loose or damaged connection in the wiring that links the sensor to the rest of the unit.
Engineer required
This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.
Find a Gas Safe engineer
Search the official register for a qualified engineer in your area.
Gas Safe Register →Worcester Bosch models that show the A7 fault code
Click a model for the full fault code list and model-specific repair notes.
- 24 RSF Repair: £90-160
- 26 CDi Xtra Repair: £90-160
- 30i Junior Repair: £90-160
- 35 RSF Repair: £90-160
- 537i Repair: £120-220
- CDi Repair: £120-180
- CDi Classic Repair: £90-160
- CDi Highflow Repair: £120-200
- Danesmoor Repair: £90-160
- Greenstar 12i System Repair: £120-220
- Greenstar 2000 Repair: £120-220
- Greenstar 25 HE Combi Repair: £90-160
- Greenstar 25HE Repair: £90-160
- Greenstar 27CDi Repair: £120-220
- Greenstar 28CDi Repair: £120-220
- Greenstar 30HE Repair: £90-160
- Greenstar 30si Repair: £120-200
- Greenstar 8000 Repair: £120-220
- Greenstar CDi Compact Repair: £90-160
- Greenstar Heatslave II Repair: £120-200
- Greenstar i Repair: £90-160
- Greenstar R29 40 HE Repair: £150-250
- Greenstar Ri Repair: £90-160
- Greenstar Si Combi / i System Repair: £90-160
- Greenstar System Repair: £120-220
- Greenstar Utility 18/25 Repair: £120-£220
- Heatslave Repair: £90-160
- Hideaway Repair: £90-160
- Highflow 250 Repair: £150-250
- Highflow 300 Repair: £150-250
- Highflow 440 CDi Repair: £150-250
- Highflow 550 CDi Repair: £150-250
- Junior 24i Repair: £90-£160
- Junior 28i Repair: £90-160
- R30 HE Plus Repair: £120-220
- Ri 25 HE Repair: £120-220
- Worcester 25/30 HE Repair: £90-160
- WR325 RSF Repair: £120-200
- ZB 7 27 HE Repair: £120-220
- ZWB 7-25 Repair: £120-220
Source
Worcester Bosch A7 fault code information on this page is sourced and cross-checked against the official Worcester Bosch service / installation manuals for each affected model.
Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 27 April 2026