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 35 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 →Avoid the next call-out bill
A cover plan would handle faults like A7: no call-out fees, no surprise bills.
Affiliate links. We may earn a commission at no extra cost to you.
Worcester Bosch models that show the A7 fault code
Click a model for the full fault code list and model-specific repair notes.
- 26 CDi Xtra Repair: £90-160
- 532 / 537 / 542 Repair: £120-200
- 537i Repair: £120-220
- CDi Classic Repair: £90-160
- CDi Highflow Repair: £120-200
- CDi RSF Repair: £120-200
- Greenstar 12i System Repair: £120-220
- Greenstar 25 HE Combi Repair: £90-160
- Greenstar 25CDi Repair: £120-220
- Greenstar 25i (ZWB 7-25) Repair: £120-200
- Greenstar 28CDi Repair: £120-220
- Greenstar 30CDi Classic System ErP Repair: £90-160
- Greenstar 30HE Repair: £90-160
- Greenstar 30i Repair: £90-160
- Greenstar 30si Repair: £120-200
- Greenstar 35 CDi Repair: £120-200
- Greenstar 42CDi Repair: £120-200
- Greenstar CDi Compact Repair: £90-160
- Greenstar Heatslave II Repair: £120-200
- Greenstar i Repair: £90-160
- 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
- Greenstar ZWB7 Repair: £120-200
- Heatslave Repair: £90-160
- Hideaway 90 Repair: £90-160
- Highflow 440 CDi Repair: £150-250
- Highflow 550 CDi Repair: £150-250
- Highflow CDi Repair: £120-220
- R30 HE Plus Repair: £120-220
- Ri 25 HE Repair: £120-220
- Worcester 25/30 HE Repair: £90-160
- 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.
- Worcester Bosch 26 CDi Xtra manual (PDF)
- Worcester Bosch 532 / 537 / 542 manual (PDF)
- Worcester Bosch 537i manual (PDF)
Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 7 July 2026