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MT10 Worcester Boiler Timer Replacement

MT10 Worcester Boiler Timer Replacement: 5 Step Guide

Last updated on June 10th, 2024

When your MT10 timer is broken your heating will not work.

Replacing the MT10 timer (or MT10rf) on a Worcester boiler is very simple once you have removed the boiler casing.

I have been carrying out boiler replacements and repairs for over ten years and replacing an MT10 timer is very basic.

Here I’ll show you the step-by-step process for an MT10 Worcester timer replacement. This is the same process for the MT10rf model and other Worcester plugin timers.

MT10 Worcester Timer Replacement

Step 1: Remove the Boiler Casing

Removing the boiler casing can be tricky and varies on different Worcester boilers.

On this model (Greenstar 28i Junior) there were two screws on the top and two screws on the bottom that needed to be loosened or removed with a screwdriver.

removing Worcester boiler casing
Removing Worcester boiler casing

There are sometimes clips to unclip also but once the screws and clips are loosened then the casing should pull forward and off.

Step 2: Remove the Screw and Holder

Next, you need to remove the plastic holder that keeps the timer in place. It’s held in by one screw that needs to be removed first then lift the plastic holder up and off.

Worcester boiler holder removal
Worcester boiler holder screw removal

Worcester boiler timer holder removal
Worcester boiler timer holder removal

Step 3: Remove the Old MT10 Timer

Next, you must slide the timer up to remove it and then disconnect the plug behind it by pulling it straight forward.

Worcester boiler MT10 timer removal
Worcester boiler MT10 timer removal

Step 4: Fit the New Timer and Holder

Next, plug in the plug on the new timer and slide the new timer down into place.

Then refit the plastic holder above the timer and screw in the screw to secure it in place.

Step 5: Refit the Boiler Casing

This is the hardest part of replacing a Worcester MT10 timer because it can be very tricky getting the screws back in properly.

Slide the boiler casing over the boiler and screw in the screws and make sure any clips are clipped back on.

MT10 Worcester Timer Replacement Video

MT10 Worcester timer replacement YouTube video

Worcester Boiler Problems

Here are some other common Worcester boiler troubleshooting posts you can learn about:


If your boiler is not working you should always check the pressure first check the pressure. Worcester boiler pressure should be around 1 to 1.5 bar on the boiler’s pressure gauge.

In most situations, replacing an MT10 timer on a Worcester boiler is very simple and should take less than 15 minutes.

Having difficulty refitting the boiler casing is always the biggest problem in my experience. Trying to get the screws back in on the bottom screw connections can be a nightmare and is a terrible setup on Worcester boilers.

The newer Worcester boilers don’t have the screws anymore (or the silly filling loop keys) but most of them out there still 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.


What setting should I have my Worcester boiler on?

The setting you should have your Worcester boiler on depends on different things.

The standard optimum temperature settings for a boiler are typically 65 degrees for central heating and 55 degrees for hot water.

You can use this as a baseline for the temperature settings on your combi boiler and then adjust them up or down if needed.

How do you bypass a timer on a boiler?

To bypass a timer on a boiler you need to remove the timer and refit the link that was originally in the boiler connections or you can make a link with a small piece of wire.


  • 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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3 thoughts on “MT10 Worcester Boiler Timer Replacement: 5 Step Guide”

  1. Steven, plese, can you tell me how the gas boiler Worcester MT10 and Worcester Greenstar Sense I Intelligent Wired Room Thermostat are connected to which terminals?

  2. Many thanks for the article.

    My elderly neighbour was quoted £200 to replace his timer. Then, when the guy came out, he tried to get him to agree to a full service plus timer replacement for £400+.

    Now we can just get a timer (£60-70) and do it ourselves 🙂

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