Worcester boiler problems

Worcester Boiler Problems: Troubleshooting Help Guide

Last updated on April 12th, 2024

Worcester boiler problems, like most boilers, are not uncommon and can be a nightmare when they cause your boiler to break down on a cold winter night.

I have been fitting and fixing boilers full-time for over a decade and have fixed my fair share of Worcester Bosch boilers.

In this post, I’ll go through some of the many problems I come across based on my experiences when I get called out to repair a boiler.

Troubleshooting Problems

Here are some Worcester Bosch boiler faults and issues that I have come across on many jobs and what you can do to try and troubleshoot these issues.

Boiler Not Turning on

A Worcester boiler not turning on could be for many reasons and there are many ways you can troubleshoot yourself.

  • No Power Supply: If you have no lights on the boiler at all, you probably have no electric supply to the boiler. You should make sure you have credit if you have a prepayment electric meter, check the circuit hasn’t tripped at the consumer unit, and check the fuse in the spur and boiler.
  • No Gas Supply: Check the gas is turned on at the meter and that you have credit if you have a prepayment gas meter. You should check if other gas appliances are working if you have any, as this will confirm if you have gas or not.
  • Thermostat Problems: Check that the temperature is turned up higher than what the room temperature is. Check the batteries in the thermostat if it’s wireless.

This is some simple Worcester boiler troubleshooting you can easily check.

No Hot Water

Having no hot water from your Worcester boiler but your heating is working could be happening for many reasons.

Here are the most common:

Combi Boiler

  • Diverter valve stuck or faulty
  • Plate heat exchanger blocked or covered in limescale
  • Faulty temperature sensor
  • Faulty flow/micro switch

How Water Tank (Cylinder)

  • 2 or 3-port valve is stuck or faulty
  • Cylinder thermostat is turned down or faulty
  • The programmer/timer is not working properly

Boiler Leaking Water

Unfortunately, Worcester Bosch boilers have a few common leaks, probably more than any other boiler that I know of.

Here are some common recurring Worcester-specific boiler leaks I come across:

  • Flow turbine adaptor
  • Flow unit left-hand block
  • Right-hand block

Whichever one of these parts is leaking will need to be replaced to fix the leak.

The flow turbine adaptor is the most common cause of a Worcester boiler leaking water in my experience.

Worcester boiler flow turbine adaptor leaking
Flow turbine adaptor leaking

Low Pressure

A Worcester boiler with a low pressure problem is most often caused by bleeding the air out of radiators, having a leak on the system, or when the expansion vessel has no air in it.

To fix this, you will need to repressurise the boiler by adding water to the system via the filling loop.

If the pressure keeps dropping too low then you will need to find and fix the problem that’s causing it to drop.

You could have a leak anywhere on the heating system, or the pressure relief valve might be letting the water outside.

Low pressure on Worcester boiler gauge

Boiler Reset

First off, whenever you are having problems, whether it’s lights flashing or just not working, you should reset the boiler.

Resetting it can sometimes save the day when the boiler has gone to lockout as it can happen when there aren’t any issues. It could also be an intermittent problem and resetting it could get it going again until you get it repaired.

The Worcester boiler reset process (unlike some other boilers) is straightforward as you press the reset button on the front of your boiler and hold it in for around 5 seconds.

If it doesn’t have a reset button, you should check the boiler’s manual for resetting it.

Worcester Boiler Reset

Flashing Blue Light

The flashing blue light on a Worcester boiler is to tell you there is a fault with the boiler, or the boiler has been put into service mode.

The flashing blue light usually means it has a fault and should accompanied by a fault code.

Frozen Condensate Pipe

If it’s sub-zero temperatures outside and the boiler isn’t working, there is a good chance it’s because your Worcester boiler condensate pipe has frozen.

This can be easily thawed out by pouring hot water over the plastic pipe outside and resetting the boiler.

Fault Codes

Worcester boiler fault codes are a great way to find out what might be wrong with the boiler when it goes lockout.

The fault codes will give an engineer a great starting point when fault finding to help diagnose and fix the problem and often help us find the issue very quickly.

Here are some of the most common Worcester boiler fault code errors:

  • 227: No flame detected. Possibly caused by a frozen condensate pipe or no gas supply.
  • A21: No signal between your wireless thermostat and receiver.
  • E9: The safety temperature thermostat has tripped. This means something is causing the pipes to get too hot, (possible blockage or pump failure) or the actual safety thermostat is faulty.


Worcester Bosch boilers are a well-made and trusted boiler but they have problems like every other brand.

There are some simple troubleshooting you can try to fix your problems like making sure you have gas and electricity to the boiler, making sure the pressure is good, and resetting it should be the first thing to do.

Feel free to ask me any questions in the comment section below and I’ll try my best to help.

Please share this post if you find it helpful.


Why does my Worcester boiler keep firing up when the heating is off?

Your Worcester boiler will fire up randomly when the heating is off when the hot water preheat function is activated.

You can turn this off by turning on ECO mode but the preheat will keep some water hot so it comes out of the hot tap quicker.

What is the life expectancy of a Worcester boiler?

The average life expectancy of a modern Worcester Bosch boiler is 10-15 years.

This can vary a lot and having a magnetic system filter can help to make it last longer.

But, if you are having regular breakdowns and having to replace parts on a boiler older than 10 years old, you should probably think about replacing the boiler.


  • Steven Reid

    I am a full-time plumber and Gas Safe registered engineer. I incorporated Housewarm Ltd. in 2011 to provide heating and plumbing services to homes in Newcastle upon Tyne, England. I now blog about what I've learned over the years to help DIYers and plumbers.

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1 thought on “Worcester Boiler Problems: Troubleshooting Help Guide”

  1. Lynda Brindley

    Hi Steve,
    Jut read your informative posts, thanks. Came back yesterday from stressful 6 weeks away to no heat/hot water. Tried resetting my Worcester Bosch as per manual several times, but not responding. (When I first manually increased control panel temperature in the room boiler fired up and radiator started to get warm, however didn’t last long and I proceeded to reset several times.) Nowhere on my boiler is there a fault panel, which puzzles me. Got up this morning and red and blue lights still flashing. Hope you can give me bit more advice please as not heard back from heatingengineer who fixed boiler when pressure problem over a year ago. Also difficulty trying to find someone else in my area. I regularly have to fill up water so presume still have air problem. My house is so cold and draughty, hope you can help! Thanks so much, Lyn

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