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Common Alpha Boiler Problems


Alpha Boilers is an international boiler company popular for designing and producing quality boilers. For more than three decades, Alpha Boilers has been operating in South, North, and Central America, Asia, Africa, the Caribbean, and the UK.

But despite the company’s commitment to excellence, Alpha boilers develop faults. Imagine waking up one morning to no hot water, or loud banging noises, or even an unresponsive boiler. What do you do? Well, Alpha boilers have built-in fault errors designed to make boiler diagnosis easier.

Red Light is on (A Indicator)

The most common Alpha boiler problem is yellow/red lights appearing on its display. You know the cause of the problem depending on the light that flashes and how it flashes.

But even then, the Alpha boiler might display a 47 error code shown on the boiler display. This error means there’s reduced burner output which could be caused by:

  • An air block in the heat exchanger.
  • Pump fault.
  • Flue fault.
  • A block in the primary flow.

When the A indicator lights a solid red, it means the burner won’t light.


A quick boiler reset will fix the red light warning. Rotate the boiler switch to the third position.  After 30 seconds, the boiler will try to restart.

If the red light warning is accompanied by error code 47, you should call a Gas Safe engineer to clean the burner and unblock the system. If the burner or the heat exchanger needs replacement, and the boiler is out of warranty, consider buying a new boiler.

Red and Yellow Warning Lights (A and B indicator)

When these Alpha boiler indicators are lit, it means that the burner won’t light. However, unlike the above fault, it also means that a simple reset will not work.


You should call a registered Gas Safe engineer to inspect the burner. The engineer will either clean or replace it.

The A indicator flashes red

When the ‘A’ indicator flashes red, and the ‘B’ indicator is blank, it means there’s a problem with the boiler overheat thermostat. The flashing indicator can also be accompanied by error codes OA3, 25 and 2.

The overheat thermostat monitors boiler temperatures and helps to prevent the boiler from overheating.


You cannot fix an overheat thermostat yourself. We recommend hiring a Gas Safe engineer to diagnose the cause and fix it. The cause could be either one of the following:

  • Faulty pump.
  • Blocked flue.
  • Airlock in the heat exchanger.
  • Faulty flue sensor.

No hot water

The state of your Alpha boiler says a lot about why you are not getting hot water. For example:

  • Is the boiler firing up?
  • Does the boiler have power?
  • Is the fun running before the boiler lights up?
  • Once it lights up, does it continue running, or does it cut out?

All the above represent different causes and problems. But if your boiler doesn’t have any of the above problems, there’s a high chance you have a faulty diverter valve.

This is the case if you don’t have hot water, but the heating works.


At times, you can free a stuck diverter valve. However, if the Alpha boiler is old, consider replacing the diverter valve. And if the boiler is out of warranty, installing a new boiler is a better option. This is because diverter valves replacement costs average £350, including labour and parts.

Low boiler pressure

It’s normal for boilers to lose water pressure over time. But if you find yourself repressurizing your Alpha boiler too often, there’s an underlying problem.  Alpha boilers display an E10 error code when the boiler pressure drops to about 0.8/0.6 bar.

The loss of boiler pressure is not always caused by a leak in the boiler. It could also be anywhere on the radiator, pumps, expansion vessels, and pipework.


Top up the boiler through the external filling loop, and the error code will clear. However, you still need to locate the source of the leak. Depending on where the leak is, it could be causing further damage to your system.

For external leaks, using a central heating system sealant will work. However, for internal leaks, you should call a registered Gas Safe engineer.

Lukewarm water

Your boiler could be heating water, but it doesn’t get hot enough. The problem can be caused by:

  • Limescale build-up in the system.
  • Faulty NTC thermistor.
  • Faulty thermostat.

The NTC thermistor monitors boiler temperature. When the water hits the set temperature, it signals the boiler to turn off. A faulty NTC thermistor will send incorrect signals, and the water can either get too hot or fail to reach the set temperatures.

But if the NTC thermistor is working correctly, the problem could be a hotspot on the pipework. A hotspot could be created by limescale build-up in the pipes or a bend or dent close to the NTC thermistor.

The high temperatures close to the NTC thermistor trick it into thinking the general water temperatures are higher than they are. Therefore, it stops water heating before it gets hot.


A Gas Safe engineer will conduct tests on the NTC thermistors to check if they are giving correct readings. If they are okay, the engineer will flush the system to remove limescale built-up in the pipe walls.

But if the limescale build-up is on the thermistors, the engineer will either clean or replace them.

Boiler lights are off

When the boiler has power, a light on the panel lights up. If the LED goes out, there’s a problem with the electricity supply. As such, the boiler will also not ignite.


Before calling a Gas Safe engineer, ensure the power connection to your boiler is secure and that you have power. If these are okay, have an engineer diagnose and fix the problem.

Loud noises from the pipes

Hearing strange noises from the Alpha boiler is common, but it isn’t normal. Loud noises are a sign of kettling, which is caused by limescale and rust build up in the system. The build-up constricts water flow causing the steam to squeeze through the pipes with kettling noises.


A registered Gas Safe engineer will Powerflush the limescale and rust from your boiler’s system. And to prevent a future build-up, he will recommend the installation of a magnetic filter. The filter will trap the debris before it has the chance to block the pipes.

Fan Fault

Boiler fans aren’t for cooling boiler components. Instead, they create a draught which pushes harmful gases into and out of the boiler flue. When the boiler is turned on, the fan starts up before other components. The PCB must recognize the fan before it turns on.

If the fan doesn’t run, the Alpha boiler will lockout and display ‘16’ as an error code. The fan fault can be caused by loose or damaged wiring and connections of a faulty unit.


Call a Gas Safe engineer to inspect and diagnose the problem. If it’s loose or damaged wiring connections, the engineer will either secure or replace them. In the case of a faulty fan, we recommend buying a new boiler, especially if your boiler is out of warranty.

Frozen condensate pipe

Condensate pipes send wastewater into a drainage system. Getting rid of the wastewater improves boiler efficiency. As such, all Alpha boilers have condensate pipes. They are made of plastic and lead to the outside of a building.

During winter, the water flowing through the pipe is prone to freezing. When this happens, the pipe is blocked, and the wastewater is prevented from escaping. Consequently water builds up in the boiler and can result in serious problems.

Gurgling boiler noises are a sign of a frozen condensate pipe.


Locate the block and thaw the pipe by pouring warm water over it. Don’t use hot water since it will melt the plastic. Once the pipe is unfrozen, reset the boiler.

Other fault codes and troubleshooting

Fault code 10: Internal wiring error

How to fix – Call a Gas Safe Engineer for diagnosis and a fix.

Fault code 37: Low supply voltage

How to fix – Inspect the mains power supply and call a registered gas engineer for diagnosis.

Fault code 15: Internal wiring error

How to fix – Call a Gas Safe engineer.

Fault code 51: Climatic RF communication fault.

How to fix – Replace the batteries.

Fault code 43: Loss of flame

How to fix – Check the gas supply is secure, the fan speed and gas valve settings. For part replacement, call a Gas Safe engineer

How to improve your boiler’s life?

Alpha boiler warranty

Alpha Boiler’s warranty depends on the boiler model you purchase. The Combi boilers come with between 2 and 7-year warranties. The standard System boilers have between 3 and 5-year warranties, and the Alpha Regular boilers have three years.

Alpha Boilers also provide you with an opportunity to extend boiler warranty on specific models by including a Premier Pack to your boiler purchase.

To extend the boiler warranty, you should have the boiler serviced annually before winter by an Alpha boiler specialist. During the warranty period, Alpha will try to solve most boiler problems over the phone and guiding you through their online guide if you feel like handling it alone. If not, they send out Alpha boiler engineers to diagnose and solve the problem.

Alpha boiler service

A registered Gas Safe engineer should conduct the Alpha boiler service. It should be done once every year. The annual service includes:

  • Cleaning boiler parts.
  • Checking boiler pressure and correct flow settings.
  • Visual inspection for leaks or corrosion.

After the service, you’ll get a service report detailing everything they’ve done.

The annual service is important for:

  • Keeping energy bills low.
  • Preventing boiler breakdowns.
  • Safety.
  • Sustaining Alpha boiler warranty.

If you’d like a new boiler get in touch with us for free quotes from 3 Gas Safe engineers. The engineers will recommend the best course of action depending on the diagnosis and solution.

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