How to Fix Worcester Bosch H07 Fault Code (UK)
Worcester Bosch showing H07 — Low pressure. UK diagnosis, likely spare (filling loop / expansion vessel) and step-by-step reset.
What the code means
H07 on a Worcester Bosch indicates low pressure. The boiler locks out to protect the heat exchanger and, on gas faults, to comply with the Gas Safety (Installation and Use) Regulations. Always reset to confirm the code is live, not historical.
Likely spare
The most common fix is the filling loop / expansion vessel. Check the exploded diagram against the GC number on the data plate before ordering — Worcester Bosch revised parts on Worcester Bosch units mid-production.
Fix procedure
Repressurise to 1.2 bar. If drops, test EV precharge at 0.75 bar.
Log the fault and reset. If the code returns within 24 hours, escalate to full electrical diagnosis with a manometer and multimeter.
Frequently asked questions
- Can I reset H07 myself?
- You can press the reset button up to 3 times. If H07 returns, the boiler needs a Gas Safe engineer — it is illegal to repair gas components without registration.
- Is the part covered under warranty?
- Worcester Bosch standard warranty is 2–10 years depending on model. Registered installations get the full term. Check the sticker inside the case.
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