Sabre Boiler Red Light On – Why?

In today’s edition of, “Why don’t my things work?!” we’re gonna be talking about boilers. Specifically, we’re discussing Sabre boilers today. While these are (usually) top of the line boilers, it is an occasional happenstance that they stop working. If your Sabre boiler’s red light has turned on it can mean one of two things, and one is certainly a better thing to hear than the other.

If your Sabre boiler’s red light has turned on, it means there’s either an issue with its pressure or that the boiler is nearing the end of its life.

Those two problems are about as opposite as they can get, so let’s talk a bit more about it to clear a few things up, shall we?

Sabre Boiler Red Light: Why?

As I said above, a red light on your Sabre boiler can mean one of two things. The better of the two solutions is that the red light is flashing. This means that there is an issue with the pressure of the boiler. To fix a flashing red light, you need to repressurize your boiler and restart it – easy!

However, if you’re noticing that the red light is on all of the time, it’s a sign of an appliance overheat failure. This means that, at some point along the line, your boiler overheated and will need a repair under warranty.

With both of these issues, there are some common symptoms you may experience:

  1. Boiler cuts out, seemingly at random
  2. Status indicator light is red (flashing or solid)
  3. Boiler can be reset and functions for a few minutes, then turns off.
    1. If it’s a pressure issue, the light will switch back to green temporarily and then flash red again once it’s heated.
  4. And a big indicator that the next section will be needed – your boiler pressure is below 1 bar. Ideally, you should have your boiler’s pressure between 1 and 2 bar (1.5 being the goal).

There are a lot of other symptoms that various people on the internet reported, but everything boils (Ha! Boiler jokes) down to the following. Sabre boilers have a sequence that they need to do certain processes in. When something along the line of that process is damaged, faulty, or failing, the sequence breaks down. Generally, you can trace the problem part(s) by following along with the boiler as it starts up, tracking specifically when it fails. This (in theory) should lead you to the specific problem.

Repressurising a Sabre Boiler

First things first – go check your boiler’s pressure (like we mentioned above). If it’s below 1 bar, you’re going to need to repressurise your boiler. Don’t worry – it’s a lot easier than it sounds. If you work visually, click here for a video guide. To repressurise your boiler, do the following:

  1. Turn your boiler off.
  2. Go to the back of your boiler. There should be two pipes that each have a small coloured lever. (They’re generally black and blue, or red and blue.)
    1. Depending on the model, these could be located on the bottom of your boiler, though they’re usually on the back.
  3. The levers should both be perpendicular (at a 90° angle) to the pipes. Turn them so they’re both parallel with the pipes.
  4. You’ll hear a rushing air/water sound – this is good. Watch your boiler’s pressure gauge and turn the levers back to the “closed” position they were in before once it reaches 1.5 bar.
  5. Turn the boiler back on and test it by running hot water through a nearby tap. If everything returns to normal within the next minute – good job, you fixed it!
    1. If your boiler begins to lose pressure again, doesn’t deliver hot water, or water turns back to cold after several minutes, it’s time to call in the big guns.

You can follow up on the repressurisation by restarting your boiler to ensure all is well. To reset the boiler, turn the mode selector to 0 for ten seconds, then turn it back to “DHW” or “DHW&CH.” This should give your boiler a hard reset, clearing any software issues that may be hiding.

When to Call for Help

There is one more thing you can do – bleed your radiators (if you have them). This is a very simple process that we cover in our “radiator pipes cold” article. Once you’ve bled your radiators, repressurised your boiler, and reset it, there’s not much more you can do. If your problems persist, it’s more than likely that something along the line has failed and will need to be replaced.

This is not a job for the layman. Boilers combine electricity and extremely hot water – it is dangerous to repair them without the proper training and experience.

If you’ve tried everything in this article to no avail, it’s time to throw in the towel. Call a Gas Safe engineer to take a look. Not only will they fix your boiler much more quickly, but they’ll do it safely. Never, ever hesitate to call a professional to fix something in your home – they’re there to make your life easier.

Final Thoughts

When your Sabre boiler’s red light turns on, it can be a bit panic-inducing. After all, red lights generally don’t mean that things are all good in the neighbourhood. Just remember to keep calm and work through each thing that may be wrong. Begin with inspecting your boiler – is the pressure gauge within the safe range of 1-2 bar? If not, repressurise your boiler and give it a reset.

If that doesn’t work, bleed your radiators, repeat the process of repressurisation, and hope for the best. If all else fails, don’t be afraid to call for help. Reach out to a Gas Safe engineer, make yourself a drink and find your favourite seat, and sit back while the professionals do what they do best – their job.

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About the Author Harry Thompson

Involved in home renovations throughout his life, Harry is an expert in everything to do with home and garden DIY. In his spare time, he enjoys cooking and tending to his garden.