F0 on a Worcester Bosch is an internal failure. The appliance has detected a fault in its own control electronics rather than in the heating system around it.

It is worth one reset, because these can be transient. If it comes back, it is engineer work.

What F0 actually means

F0 is a broad code. It means the boiler has found something wrong internally that does not fall under one of the more specific fault codes.

Because it is broad, it cannot be diagnosed from the code alone. It gets tested.

What you can safely check yourself

Press and hold the reset button for three seconds and release it. If the boiler restarts and runs normally, it may have been a transient glitch.

If F0 returns, stop there.

When to stop, and why

What causes it beyond the simple checks

Most commonly a fault on the PCB itself, or a damaged connector or lead assembly between the board and the rest of the appliance. The service booklet takes the engineer to the PCB after checking whether the reset button is flashing and inspecting the 20-pin connector lead assembly for damage.

How Vantage can help

We are Gas Safe registered under 956889 and cover Hertfordshire, Bedfordshire and Cambridgeshire, with an emergency line answered 24 hours a day. Call us on 01462 506374. See also boiler repair and boiler servicing.

Frequently asked questions

Does F0 mean a new PCB?

Often, but not always. Damaged wiring or a poor connector can produce it, so those get checked first.

Is F0 dangerous?

It is not a combustion or overheat fault. The boiler has stopped itself, which is the safe outcome.

Is it worth repairing an older boiler with F0?

That depends on the age and condition of the appliance. We will give you the repair price and an honest view on whether it is worth spending, and you decide.

Related fault codes

Other Worcester Bosch codes: EA · C6 · E2 · Fd · all Worcester Bosch codes. See also boiler repair and how long does a boiler last.

In Worcester Bosch’s own words

Worcester Bosch use different code sets across their ranges and generations. The definition above is taken from the Greenstar CDi Classic service booklet. If your boiler is a different model and the code behaves differently, check the manual for your appliance or ring us and we will tell you what it means on your unit.

When to call an engineer

If the checks above have not cleared it, the next steps are engineer work and the boiler should not be reset repeatedly in the meantime. Call Vantage Plumbing and Heating on 01462 506374. We are Gas Safe registered under 956889, the line is answered by a person at any hour of any day, and you get a price before anyone starts.

Need help today?

Call and speak to a person, any hour, any day of the year. Get a fixed price quote or call 01462 506374.