How to Fix Worcester Bosch D5-273 Fault Code (UK)
Worcester Bosch showing D5-273 — Flow temp sensor. UK diagnosis, likely spare (flow NTC 87161066660) and step-by-step reset.
What the code means
D5-273 on a Worcester Bosch indicates flow temp sensor. 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 flow NTC 87161066660. 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
Drain to pin, unclip sensor, refit with new O-ring.
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 D5-273 myself?
- You can press the reset button up to 3 times. If D5-273 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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