The 6 Most Common Fan Faults With Modern Boilers

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Boiler Fan Fault Problems And Cures Common Q & A

In this article, we’re going to cover common faults with fans on modern boilers.

Boilers use a fault code and lock out system. When the boiler recognises a problem, it’s going to stop working (lock out) as a precautionary measure.

In some cases (for instance, there’s a possibility of a gas leak), this is to protect the people living in your property from danger. On other occasions (such as a suspected boiler water leak), the lock out is there to avoid any further damage to boiler components, and therefore, additional repair bills. Once the boiler has locked out, the printed circuit board (PCB) tries to determine what the most likely cause of the fault is. It will then display a fault code on the display panel.

This helps a Gas Safe engineer to quickly identify what the problem is with your boiler. By using the fault code for guidance, the fault-finding mission is much quicker than if they didn’t have any indication of the fault, and therefore saves them time; that makes the repair much cheaper.

Just below is a typical list of questions which we do our best to answer further in the article.

Boiler Fan Fault Problems

  • Will resetting my boiler fix the fan fault and clear the fault code?
  • Is my boiler dangerous if there is a problem with the fan?
  • What does the fan on my boiler do?
    • Loose connections on the wiring harness
    • The fan’s speed is too low
    • Water has leaked on wiring and connections
    • The fan isn’t working
    • Airway faults
    • Intermittent operation of the boiler’s PCB
  • How much does it cost to fit a new fan on my boiler?
  • If I need a new fan, should I replace my boiler instead?

Will resetting my boiler fix the fan fault and clear the fault code

As well as a fault code and lock out function, boilers have a reset function. But, this isn’t there to be used as a fix for a fan fault, or any other fault for that matter.

If you reset your boiler without fixing the fault, there’s a chance that you might trick the boiler into working, for a few minutes or more. While it’s working, it could be dangerous or damaging internal components.

So, don’t try and reset your boiler. Instead, call a Gas Safe boiler repair company. Once they’re confident that the issue has been found and fixed, they’ll be able to reset your boiler to clear the fault code on the display panel and get your boiler working again.

Is my boiler dangerous if there is a problem with the fan

If the fan on your boiler isn’t operational or isn’t working at its optimum, there’s a chance that it could be dangerous. And, that’s exactly why the lock out function is incorporated into boilers. In its locked-out state, it’s unlikely that your boiler is dangerous.

If you can see a fault code being displayed and it relates to a fan fault, your boiler should lock out. If it’s not locking out, there’s the potential for your boiler to be dangerous. Whilst it’s likely a Gas Safe boiler repair company can fix this quickly, it’s worth turning off your appliance in the meantime.

What does the fan on my boiler do

The fan on your boiler, from a safety perspective, is one of the most important components. It doesn’t act like a fan on other machinery, such as cars (i.e. cooling the car’s engine down). Instead, the fan on a boiler helps to drive harmful gases out of the flue. Without the fan, these gases would linger and become dangerous.

In fact, the operation of the fan on a boiler is so important, the boiler won’t fire up, until it recognises that the fan is operational.

The PCB is the brains of any boiler. It communicates with all the electronic components in your appliance, as well as a range of sensors. One sensor that is directly related to the fan’s operation, is the air pressure switch. When the fan fires into life, the air pressure switch should notice a difference in air pressure. Once the boiler’s PCB sees this signal, it’s going to demand gas from the gas valve, and use the spark generator to produce a flame.

If the fan isn’t operational, it isn’t working to its full potential (i.e. gases aren’t being vented from the flue correctly), so it’s going to lock out and display a fault code.

But, if your boiler has a fan fault, what is your boiler engineer going to be looking out for?

  • Loose connections on the wiring harness

For your fan to communicate with the PCB, it’s needs to be connected via a wiring harness. So, this is going to be the first thing that your boiler engineer is likely to check.

If there’s a problem with wires and connections on the wiring harness, signals aren’t going to be passed correctly from the fan to the PCB, and vice-versa.

Faults here can come in the form of damaged wiring, or loose connections. Your Gas Safe boiler engineer will be able to visually inspect all aspects of the wiring and connections to and from the fan, and check if there’s any obvious breaks in the circuit.

On some occasions, replacing small sections of wiring, or simply securing connections that have come loose, is all that’s needed for signals to be efficiently moving between the fan and PCB.

If the issue is loose connections or wiring, it’s likely there has been a fault that’s contributed to the problem. Whilst your boiler is going to vibrate due to its many moving parts, some parts can start to vibrate excessively over time. These components need to be found and fixed, otherwise the problem will reoccur.

Typically, we find that the fan and the boiler’s pump are the components that are most likely to vibrate excessively.

As both parts spin on a shaft, they need bearings. And, bearings can wear out over time. As they wear out, they break down. Instead of helping the component to spin smoothly, the bearings grind. This is likely the issue if you’ve heard strange grinding noises from your boiler.

On some occasions, it makes sense to get a service kit and replace the bearings. But, if the pump/fan is in poor condition, a replacement component would be a much wiser option.

  • The fan’s speed is too low

We’ve already mentioned that the fan on your boiler needs to push dangerous gases out of the flue. For that to happen, it needs to be operating at the correct speed. If the speed of the fan is too slow, any kind of back draught into the flue (strong winds, for instance), is going to result in gases being pushed back into the boiler.

Most people think that strong winds can blow out the pilot light on a boiler, but that’s not usually the case. The air pressure switch wants to recognise air pressure being pushed out of the boiler by the fan, not backwards, into the boiler. When it recognises this issue, it effectively tells the PCB that the fan isn’t working.

And, just as a boiler won’t fire up without the fan working, if at any point the PCB receives the signal that the fan has stopped working during operation, it’s going to cut gas supply to the gas valve. In turn, that means the pilot goes out. So, whilst strong winds don’t directly “blow out” a pilot light, they are a contributing factor to the boiler’s PCB taking the decision to cease operation.

The fan’s speed can be adjusted by a Gas Safe engineer. But, it’s only likely to be a problem on a new boiler, or one that’s been fitted in a new location. If neither of those scenarios sound like yours, the only other possibility is that there’s a problem with the fan’s operation, due to wear and tear. A typical example would be worn bearings, that aren’t allowing to the fan to work at its operating speed.

Your boiler engineer will be able to inspect the fan, and determine if it can be adjusted, repaired, or it needs replacing to fix the fault and clear the fault code being displayed on your control panel.

  • Water has leaked on wiring and connections

Loose connections on your fan are one thing, but damage from water leaks is another. Unfortunately, water leaks on modern boilers are more common than you might think, and there are a few culprits.

The important thing here, is that the wiring and connections that have been affected by the water damage on your boiler don’t just need to be fixed, the leak needs to be fixed too.

So, your Gas Safe heating company will need to find all the sections of wiring and connections that have been damaged. To ensure that all the damage has been highlighted, they’ll use a multi-meter. This helps to show where there are breaks in the circuit, or where there’s a weakness in power.

Once they’ve fixed all the electrical issues, they’ll need to focus their attention on the leak.

Internal boiler leaks typically come from two components; the pump and the heat exchanger.

The pump is likely to leak due to old age, set on too high a pressure, or has a build-up of heating sludge. All these things can contribute to the seals deteriorating. Once these seals deteriorate, that’s going to lead to small leaks. And, it’s the water from these leaks that finds its way into a range of electronic components.

So, fixing the leak won’t just ensure that the fan doesn’t get damaged again, it’s going to ensure that other electronic components aren’t damaged too.

If the pump is beyond repair, your boiler repair company is going to suggest a replacement. A replacement pump from a leading brand such as Grundfos is going to cost in the region of £250.

Moving onto the heat exchanger, the most likely cause of the leak here, is going to be limescale build-up on the plate. Where there’s limescale build-up in any part of the heating system, it’s going to burn hotter than it should. Over time, this weakens the plate on the heat exchanger, and the plate eventually cracks. This leads to a small leak.

Unfortunately, the heat exchanger on your boiler isn’t a particularly cheap part to replace, and it’s rare that they can be repaired. You should expect a heat exchanger replacement to cost somewhere in the region of £400-500, depending on your boiler.

  • The fan isn’t working

Not all fan faults are ones that are worth fixing. If your fan has been working intermittently, you’ll have noticed fault codes that are related to the fan’s operation being displayed on a regular basis. Eventually, the fan is going to stop working completely.

Like any mechanical component, it can be reconditioned. The main question to ask your boiler engineer; is it worth it?

Fans aren’t the most expensive part on a boiler to replace. After you’ve paid for parts and labour to fix a fan, there’s a good chance that the most logical long-term option is to simply replace the fan.

  • Airway faults

Whilst most fault codes might seem specific, that’s not always the case. Most fault codes that relate to the fan simply state that the fan isn’t running, but that doesn’t mean the fan isn’t working. It could’ve been told to stop running by the PCB.

As we mentioned, the air pressure switch is a component that makes sure dangerous gases are being vented out of the flue. When they’re not, it recognises the issue, and feeds back the signal to the PCB.

So, if your boiler engineer can’t find a problem with the fan, they need to check for airway faults. And, the first thing to check, would be that the air pressure switch is feeding the right signals to the PCB. After all, if the air pressure switch isn’t working correctly, it’s unlikely that the signals that it’s giving to the PCB are the right ones. Your boiler engineer will be able to test the air pressure switch using a multi-meter.

After ensuring that the air pressure switch is functional, they’ll look for physical airway blockages. They’ll need to check both the flue and condensate pipe. If either of these are blocked with debris, that’s going to adjust the air pressure in the boiler to a level that the air pressure switch deems out of tolerance, leading to a fault code being displayed and the boiler locking out.

If there is a blockage (such as debris in the flue, or a condensate pipe that’s frozen), your boiler repair company will need to clear the blockage and then reset the boiler to clear the fault code.

  • Intermittent operation of the boiler’s PCB

If all else fails, your boiler engineer will want to start testing the PCB. The PCB is the heart of any boiler. Any malfunction (no matter how small), is going to lead to intermittent operation of your boiler.

Most boiler engineers will run a quick diagnostic on the PCB, as any electrical fault (regardless of what fault code is being displayed), could be connected to this component. If the PCB is faulty, the fault codes it’s displaying could be wrong.

If your PCB is failing, it’s going to work intermittently, and that might mean that the:

  • Display panel lights working intermittently
  • Heating and hot water not getting up to temperature
  • Boiler is cycling on and off for no reason

And, it’s likely that the issue that’s caused a fault with the PCB, is connected to a fan fault as well. For instance, water damage or excessive vibrations (mentioned above) are going to affect all fragile electrical components in your boiler, including the PCB. By fixing these vibrations/leaks, you’ll protect all components from further damage, not just the original culprit.

After testing the PCB using a multi-meter, your boiler engineer will be able to determine whether it’s salvageable. If it’s not the replacement cost is going to be somewhere in the region of £450-550, depending on the exact boiler that you own.

How much does it cost to fit a new fan on my boiler

The cost of a replacement fan is going to vary, depending on where you are in the country, and the exact boiler you have. For instance, labour rates in London, tend to be much higher than that of the Scottish Highlands. Likewise, a fan for one boiler (parts only), could be twice the price of one for another.

That said, you should expect to pay somewhere in the region of £200-300 for a replacement fan on your boiler.

If I need a new fan, should I replace my boiler instead

But, you shouldn’t replace your fan without consulting your Gas Safe registered heating company. If your boiler is old and out of warranty, as well as the fan, other components might be on their last legs. The last thing you want to do, is to spend £200 or more on a repair, to find that lots of other components fail, just months down the line.

So, it’s worth asking your heating engineer to do a basic inspection of all the important components in your boiler and determine their condition. This includes components such as the:

  • PCB
  • Gas valve
  • Heat exchanger
  • Air pressure switch
  • Burner

If the fan, as well as one or more of these components is likely to fail soon, it’s likely that a replacement boiler is a much better option. A new boiler will come with a long parts and labour warranty, as well as being extremely efficient in comparison to your current boiler, saving you money on energy bills.