Glow worm f9 fault code on boiler

What does the Glow Worm F9 Fault mean?

Glow Worm boilers display the F9 fault code. This indicates that there is a problem with the pressure. Glow Worm states in the boiler manuals that it is most likely caused by a problem with the water pressure sensor. However, low pressure can also cause this issue.

The water pressure sensor measures the boiler’s pressure and sends them to the printed circuit board (PCB).

The PCB is the central hub of the boiler’s electrical operations. It must be confirmed that every stage has been completed safely before it can signal that the next step can begin.

If the pressure sensor registers above or below the recommended reading, then the PCB will shut down the boiler and display the fault code F9 on a Glow Worm boiler.

If the PCB cannot receive readings from a pressure sensor, this can also occur.

The code could also indicate that your system is experiencing a reduction in pressure. You may not need to replace any of the parts, but this code could indicate that there are faulty parts.

A leak can be detected if there are frequent or significant drops in pressure.

What’s Boiler Pressure?

Heating systems can be characterised by two types of pressure: one is gas, the other water.

People usually refer to “boiler Pressure” or “system Pressure” when they talk about water. This is also true for the Glow Worm boiler F9 fault code.

Water must flow at a speed that allows it to reach the Glow Worm boiler unit as it flows from the main supply otherwise you will start to get various fault codes, one of which will be the F9 error.

Pressure is the force required for water to flow at this speed. The speed of water flows at a slower rate around your central heating system if the volume of water inside the pipes is less.

This can cause water to leave your taps at a slower rate. This can cause overheating problems as your boiler only produces heat that is appropriate for the water in the pipes.

Your boiler unit may heat up if excess heat is not transferred to water through the heat exchanger.

This can lead to serious damage and even danger. The boiler will then lock out and issue a fault code t when it detects any problems that could cause overheating.

What Causes Low Pressure in a Glow Worm Boiler?

Boilers can lose pressure slowly over time. Most boilers need to be repressurised at least once a year. You can increase the central heating system pressure yourself.

Bleeding radiators can increase the risk of water escaping and cause pressure loss. This can be done at home if there aren’t any other issues. It won’t cost you a lot of money and you don’t need a gas safe registered engineer.

This is an important task to maintain your Glow Worm boiler pressure. It will help keep your boiler efficient and healthy for longer and decrease the chance of serious problems.

A leak may exist if the boiler pressure drops rapidly or doesn’t remain at the right level after being topped-up.

Sometimes, you can identify a leak. It’s worth looking around radiators and other visible areas for piping.

Also, you may have noticed damp patches on floors, ceilings, and walls. Leakages are not always visible at the surface, so an engineer is needed to inspect hidden areas of the system.

How do you check the pressure of a glow worm boiler?

A lot of boilers come with a dial at the front, known as a pressure gauge. This will show the boiler’s current pressure in bars.

Some Glow Worm boiler models have a digital display, but this doesn’t always show the reading. To access the pressure, click:

  • You may have to press the reset button under the display screen.
  • It will typically show ’88’ just before the pressure reading
  • For a few seconds, the pressure will be visible

The recommended reading for cold systems is between 1 and 1,5 bar. You can safely top up the water pressure if the display shows less than 1.5 bar to check if the F9 fault code is cleared.

How do you top up the pressure on a glowworm boiler?

First, make sure that the boiler is turned off and cold. To prevent any hot pipes from heating up, it is safer for both the boiler and you.

You will find what is called a “filling loop” underneath the unit. This is a length pipe that has one or more taps attached. They are usually coloured handles to distinguish them from the pipe.

For loops with two taps turn the tap clockwise so it stops turning. Slowly turn the other tap clockwise until water is moving through.

If the pressure gauge is visible, wait for it to reach 1.5 bars and then turn off both taps.

If you are unable to see the reading, count 3 times before closing the taps. Next, bring up the reading on display and continue this process until 1.5 bars is reached.

The same procedure applies for loops with one handle. However, water will flow through the tap once you open it.

You can now reset your boiler to see if it works properly if the fault code is not displayed. You should keep track of the pressure reading while you do this. If it drops at all, it is likely that you have a leak.

Do not repressurize the unit again as this could cause damage or force water out of other pipes in the house. To fix the problem, you will need to contact an engineer.

What if the F9 Fault Code is a Faulty Pressure Sensor?

The pressure sensor is an electrical component that can easily be damaged or malfunction over time.

Engineers will often find that the water pressure sensor surface is blocked by dirt. This prevents it from reading so the Glow Worm boiler will show the F9 fault code. Sometimes, the only way to remove this dirt is to increase the pressure.

The wiring connecting the sensor and the PCB could have become loose, or even damaged. This can occur at the sensor’s end or at the point where they reach to the PCB.

After long-term wear and tear, the wiring within the boiler can become loose due to vibrations from the pump and other large parts.

These movements tend to increase with age but if there is a sudden rise in the volume of the unit’s vibrations, it could be a sign that the pump is failing.

If they are exposed to moisture, the sensor, surrounding wiring and PCB could all be damaged. Cracked heat exchangers are a common cause of leaks in the unit, which is often due to limescale buildup.

Do you need to call a Gas Safe engineer to fix the Glow Worm F9 Fault in

You will need to call an engineer if the boiler pressure is not being topped up or the system is still experiencing pressure losses.

To legally perform the work, they will need to register as a Gas Safe engineer. This involves removing the boiler unit’s cover.

A multimeter is a tool that allows them to test the operation of the pressure sensor.

These devices are used to measure resistance of wiring or parts, and can be compared with the recommended resistance.

A replacement part for a sensor that has lost its functionality will cost around PS30 plus labor costs. The cost of replacing any surrounding wires is similar.

The cost of repairing a leak will vary depending on the extent of damage.

Pipe connector leaks throughout the house can be less costly as they are easy to replace. They may require more labour costs if there is limited access to the affected areas.

Boiler unit leaks can be more expensive to repair. The leaking part as well as any other damaged parts will need to either be replaced or repaired.

If a heat exchanger crack is the cause of the leak, it can cost as high as much as £500. A new part may be required if the PCB is damaged by moisture, which can vary depending on the model of your boiler. If your heat exchanger is damaged it may be time for a new boiler.

If several components are damaged, an engineer might recommend that a boiler be replaced.

Get free quotes to fix your glowworm F9 error

faulty pressure sensors can just be the start of more problems in other components so if you have an old Glow Worm boiler it may be time for a new boiler. Glow Worms boilers sometimes come with long warranties so always check this first. Vaillant and glowworm boilers are now joined together since they were acquired so you may also see this fault code on both models.

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