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Common Alpha Boiler Problems & Repair Advice

Rob Wells
By: Rob Wells
Updated: 11th January 2022

Last Updated: 11th January 2022

Many common Alpha boiler problems can be repaired yourself in a few simple steps, but if in doubt always contact a Gas Safe registered heating engineer. You can get free boiler repair quotes using Boiler Guide.

Common Alpha boiler problems

Alpha boiler problems Possible Alpha error code
Low boiler pressure E10
Lukewarm water 37
Red light (A indicator) 47
Red light (A indicator) 2, 25 or 0A3
No lights on boiler 37
Loud noises 3, 25
No hot water 37, 16

Low boiler pressure (E10)

When the boiler pressure drops to around 0.6bar on the pressure gauge, your Alpha boiler will fail to operate. A sudden drop in pressure is a strong indication that there’s a link somewhere around the heating system. Radiators, various pumps and expansion vessels can all be prone to leaking.

How to increase Alpha boiler pressure

If there’s a leak, you shouldn’t increase the boiler pressure until a fully-qualified heating engineer has fixed the leaking component. Find out more with our guide to low boiler pressure.

Lukewarm water

As some boilers get older, some of the parts can get worn down and cause the running water to only be lukewarm.

Fixing lukewarm water

Some of the potential causes that can lead to lukewarm water include:

  • Faulty thermostat
  • Faulty thermistor
  • Blocked diaphragm
  • Faulty diverter valve

You shouldn’t attempt to fix any of these yourself, always hire a Gas Safe registered engineer.

In addition to the above faults, it could be that some of the hot water that’s meant to be going to the hot water tap, is travelling to the radiators instead. When running the hot water, check if any of the radiators heat up. If they are, the hot water thermistor might need replacing.

Red light on (A indicator)

As well as error codes, Alpha boilers also have lights to show that there’s a fault with the unit. A consistent red light on the A indicator means that the burner has failed to ignite.

Fixing the burner on an Alpha boiler

When seeing this red light, Alpha recommend turning the front boiler switch to 3, which will reset the boiler. The boiler will then make an attempt to restart 25-30 seconds later.

If this doesn’t work and the boiler still won’t ignite, you’ll need to hire a Gas Safe registered engineer to clear the burner of any debris.

Flashing red light (A indicator)

Seeing a flashing red light on the A indicator means that there’s an issue with the overheat thermostat. You might also see a 2, 25 or 0A3 error code.

The overheat thermostat is a vital part of Alpha boilers as it monitors the temperature to prevent the unit from overheating.

Alpha overheat thermostat fix

An overheat thermostat isn’t something you can fix yourself, always hire a Gas Safe registered engineer who will diagnose and fix the fault, which could be one of the following:

  • Heat exchanger airlock
  • Faulty pump
  • Flue sensor issue
  • Blocked flue

No lights on boiler

When there’s power to your Alpha boiler, there will be a light, should this go out then it means there’s an issue with the supply of electricity to the boiler. This will not only mean that it fails to light up but also ignite.

How to get power back to the Alpha boiler

Check to see if other electrical appliances around your home are working, if they’re not then there could be an issue with the electricity supply. You should contact your electricity supplier, who will be able to advise. In the case that other appliances are still working, it’s time to call an electrician who will be able to diagnose and fix any issues with the supply of electricity to the boiler.

Loud noises coming from the pipes

Hearing some strange and unfamiliar sounds from your boiler can be a strong indication of kettling, which is generally caused by a buildup of limescale, rust and other debris. This buildup prevents water from flowing around the heating system, which can lead to it boiling, steaming and then making noises resembling a kettle.

How to fix loud noises from an Alpha boiler

A heating engineer will be able to clear your heating system of any debris by flushing chemicals around the system in a process known as a powerflush. To prevent this buildup from happening in the first place, a magnetic filter can be fitted, which catches any debris in the water before it has chance to block the water from circulating.

No hot water but heating works

If you find that the central heating is turning on when you want hot water, this is likely to mean there’s an issue with the diverter valve. The diverter valve directs hot water to either the central heating or hot water taps, depending on which you want at the time. From time to time, especially when it comes to older boilers, the diverter valve can get stuck, meaning that all the hot water is sent to the central heating rather than the taps.

How to fix a diverter valve

A diverter valve that’s stuck in one position can often be unstuck but there’s a chance that the whole part might need replacing. Either way, you should hire a Gas Safe registered engineer to diagnose and repair the fault.

Need a boiler repair?



Which Alpha boiler problems need a heating engineer?

Not sure which boiler issues you can tackle yourself? Take a look at the table below to see the most common boiler problems, what they might mean, and whether you'll be needing an an engineer.

Problem Possible cause Do you need an engineer?
No heat or hot water Broken diaphragms and airlocks, failure of motorised valves, issues with the thermostat or low water levels Yes
Leaking and dripping Most common cause is a broken internal component but it will depend where the water is leaking from Yes
Banging, whistling or gurgling noises A common cause is air in the system, alternatively it could be that the water pressure is too low or it's kettling Yes
Pilot light goes out Could be a broken thermocouple which is stopping the gas supply Yes
Losing pressure There could be a water leak in the system, the pressure relief valve needs replacing or the radiators have been bled recently No, unless there's a leak
Frozen condensate pipe Your boiler should display a fault code or warning notification Yes
Thermostat issues Thermostat may be turned off or not set to the correct settings (time etc.) Consider replacing
Kettling Limescale or sludge building up on the boiler's heat exchanger Yes
Radiators not getting hot Sludge or air build up in the system or an unequal distribution of heat You will need to bleed the radiators which doesn't require an engineer unless you don't feel like carrying out the task yourself.
Boiler keeps switching itself off Could be low water pressure, a problem with the thermostat or a lack of water flow due to a closed valve, air in the system or the pump not circulating the water in the system correctly Yes

Alpha boiler warranty

The warranty of Alpha boilers depends on the model you decide to install in your home. Their Combi boilers come with 2-7 years warranty, 3-5 years as standard for System boilers and 3 years on their range of Regular boilers. Alpha also offer the opportunity to extend a warranty on some models by adding a Premier Pack to your purchase. Know exactly what to expect with our complete guide to Alpha warranties. To keep the warranty valid, you’ll need to arrange for your Alpha boiler to be serviced annually by a Gas Safe engineer.

Boiler insurance and ongoing cover

Taking out boiler insurance once your boiler warranty has expired is a option worth considering. This can be done with your energy supplier but there's absolutely no obligation to do so. When comparing boiler insurance, keep an eye out for ones that offer annual service and safety inspections.

Is it time to replace your Alpha boiler?

If your Alpha boiler was installed a long time ago then it could be time to consider a new one. Installing a brand new boiler could save you up to £365* a year in a detached home. Take a look at the table below to see how much you could be saving depending on your current boiler rating and property.

House Type G (< 70%) F (70-74%) E (74-78%) D (78-82%)
Semi-Detached £240 £170 £150 £135
Detached £365 £255 £205 £165
Detached Bungalow £190 £135 £120 £105
Mid Terrace House £205 £145 £130 £115
Flat (Mid Floor) £95 £65 £60 £50

Figures are for England, Scotland and Wales only*.

Who can replace an Alpha boiler?

If you think that it's time to part with your current boiler and install a new one then the next thing you have to decide is who you'll be choosing to replace it, a local engineer or a national company.

Branded manufacturers may cost a little bit more than local engineers but you'll be covered by big brand protection, which is a huge bonus, and they could provide extra services, including ongoing boiler cover.

Local engineers can offer very competitive rates and you'll get a personal service from the same person throughout your installation. When considering engineers, don't go with the first quote you receive, we recommend getting up to 3.

Send us an enquiry today to receive free quotes for a new boiler and find trusted engineers near you with our free service.

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Data Source: Energy Saving Trust, Heating Your Home: Boilers (2022)
*Based on replacing an old gas boiler with a condensing A-rated boiler with thermostatic radiator valves, programmer and room thermostat in a detached home. Figures are based on fuel prices as of November 2021.

Rob Wells

About the author

Rob Wells

Rob is another of our resident home heating experts. He manages our external partnerships, making sure you get the most up to date information.

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