Error No light

Safety precautions:

- If you smell gas, leave the property immediately and call the gas emergency number from a safe location. Do not operate electrical switches or the boiler.

- Isolate the boiler’s electrical supply before removing any covers or attempting internal inspections. If you are not competent with electrical work, do not open the boiler.

- Do not attempt to modify or repair the gas, ignition or PCB components unless you are a Gas Safe registered engineer.

Initial checks a homeowner can do:

1. Check mains power to the house: confirm other sockets, lights or appliances are working to rule out a wider supply cut.

2. Check the consumer unit (fuse box) for tripped MCBs/RCDs. Reset any tripped breakers and try the boiler again.

3. Locate the boiler’s external isolator switch or fused spur (often adjacent to or beneath the boiler) and confirm it is in the ON position. If it has a replaceable fuse (e.g. 3A), only replace with the correct rating.

4. Power-cycle the boiler as Worcester recommend: turn the boiler off at the isolator, wait 10–30 seconds, then turn it back on to attempt a reset.

5. Try calling for hot water (open a hot tap) and/or set the thermostat high to see if the boiler fires even if the LEDs are off. If the boiler fires but lights stay off, the issue may be an LED/indicator fault or the PCB lighting circuit.

6. Check the boiler pressure gauge. If pressure is extremely low (well below 0.5–1.0 bar) the boiler may not operate correctly; top up following the manufacturer’s instructions if needed.

Specific diagnostic and fix steps (only progress if you are competent and confident; otherwise call a pro):

1. If there are no lights and the boiler does nothing after the simple checks above, check the fused spur supplying the boiler and any visible inline fuse. Replace a blown replaceable fuse with the same type and rating only.

2. If you have competence with basic electrical testing and appropriate tools, an electrician or engineer can verify whether 230V is present at the boiler’s supply terminals. Do not attempt voltage checks unless trained.

3. If mains power is present at the boiler but there are no display lights, the problem may be the PCB or the indicator LED(s). A single failed LED can be left alone if the boiler is otherwise operating; a PCB power problem will often result in multiple lights failing and/or boiler lockout.

4. If the boiler shows intermittent sounds (fan/pump) but then goes quiet and the green light behaves as described in some fault reports, do not try to force or repeatedly reset the appliance. Record the sequence (what you pressed, what you heard, lights behaviour) to tell the engineer.

5. Visually inspect (with power isolated) for signs of water ingress, burn marks, loose connectors or corrosion on the PCB and wiring. If you see obvious damage, isolate the appliance and call an engineer.

When to call a professional:

- If replacing a fuse or resetting the consumer unit did not restore lights or operation.

- If there is any uncertainty about electrical work or if you need mains voltage checks — these must be done by an electrician or Gas Safe engineer.

- If the boiler will not fire (no hot water/no heating) or if you suspect a PCB failure, ignition or gas valve issue.

- If there are any signs of water damage, burnt components or repeated lockouts.

Additional notes:

- If the boiler is under warranty or on a service cover, contact Worcester Bosch or your cover provider before any invasive work.

- Keep a clear record of what you observed (lights, noises, behaviour) and any steps you took — this helps the engineer diagnose faster.

- Do not attempt to bypass safety devices or operate the boiler if you believe it to be unsafe.

In short: do the basic external power checks and a simple power-cycle yourself. If that does not restore the display or the boiler is dead or behaving unpredictably, stop and arrange for a Gas Safe registered engineer (or an electrician for supply verification) to diagnose and repair the unit.