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No on/off indicator light

No on/off indicator light — Boiler appears off or unresponsive

Worcester Bosch · Greenstar Boilers

What does No on/off indicator light mean?

The blue on/off indicator light is not illuminated, and the boiler appears to be off or not receiving a signal to operate, even if mains power is seemingly present.

Common Causes

  • Momentary power failure
  • Programmer setting issue
  • Master switch is off

Repair Steps & Checklist

Click steps to track your progress.

  1. 1

    Switch off the appliance at the master switch, wait a few seconds, then switch it back on.

  2. 2

    Check the programmer settings to ensure it is programmed to call for heat or hot water.

  3. 3

    Verify that your property has a continuous power supply and that other electrical items are working.

Browse all codes in this manual (12)
Verified technical data. Last updated: April 2026

Related Faults

Blue light Fast flashBlue light Fast flash — Hot water not working (central heating OK)Blue light Fast flash 2 pulsesBlue light Fast flash with 2 pulses — Boiler not responding to any demandBlue light Fast flash 5 pulses, Reset button FlashingBlue light Fast flash with 5 pulses, Reset button Flashing — Ignition lockout
Source: Worcester Bosch Greenstar Boilers
Open Manual (Page 87)Search more codes in this manual