F73 Vaillant Boiler Fault Code Meaning & Fixes
The F73 error code refers to the water sensor. It affects the ecoTEC Plus, aquaTEC and ecoMAX models Vaillant boilers.
This F73 Vaillant error code indicates that the low water pressure sensor has been operating incorrectly. It could indicate a boiler leak or malfunctioning parts.
F73 is a minor error that can be easily fixed, however, because the boiler’s internal parts are involved a Gas Safe engineer should be called.
If your Vaillant boiler is around or over 10 years old and starting to cost in repairs, call outs and higher energy bills a new boiler may be the best option and you can read our guide to Vaillant boiler prices here for more information.
What Does a Vaillant F73 Error Look Like?
Low water pressure sensor faults can cause the F73 error code.
Boiler sensors monitor whether the boiler is operating correctly by monitoring pressure, gas flow, and water pressure. The boiler will lockout if the pressure is not correct and display an error code.
The F73 code indicates that the water pressure sensor signal has failed.
What does it mean if my boiler displays a F73/F74 fault code?
Vaillant states that the F73 and F74 boiler fault codes refer to a low water pressure sensor fault.
Both fault codes mean the same problem and it is purely and evolution in the model and brands ranges that have changed numbers.
What is the difference between two error codes for the exact same fault?
Boilers will be upgraded over the years and new models will also be available with the updated fault code number.
As the company continually updates their error code database, the fault codes for different Vaillant boilers may vary.
So depending on the boiler’s fault codes, the F73 fault code or F74 fault code will be displayed but it will mean the same thing.
What is a Vaillant low-pressure water sensor?
Every boiler has a variety of gauges and sensors. These sensors and gauges monitor the boiler’s water pressure, temperature, and air pressure.
A low water pressure sensor will display a F73 fault code if it detects that a boiler is operating outside the recommended pressures.
The water pressure sensor will look for a heating system that drops to below a specific pressure, usually around 0.6 bars.
This indicates that there is a leak in your system. It will then lock out to prevent the boiler from operating as a dry fireplace.
It’s more than a safety precaution to safeguard internal boiler parts.
Property damage is caused by a leak. A heating system that is in use creates more pressure and releases more water through the leak. This can cause more property damage.
The lockout protects your boiler and your property while you or a Gas Safe registered heating engineer work out what the fault code means.
What Causes a Vaillant F73 Error
F73 indicates that the water sensor has detected inadequate water pressure. This is often caused by a leak in the system. However, if the sensor is defective, it will give incorrect readings.
There are many reasons why a sensor might give inconsistent or inaccurate readings. The sensor could also be defective or loose (water- or other) connections to the PCB.
Loose Connections
Boilers have many vibrating parts like the fan and pump. This can lead to a loose electrical connection. As wiring connections become loose over time and less effective they can lead to more and more problems.
Water damaged wiring
A damp electrical connection or failing wiring can lead to incorrect readings. This is most commonly caused by water damage from an internal boiler. This is usually caused by damaged seals or broken heat exchangers. These leaks can cause electrical components and wiring to fail by allowing condensation to settle on them.
Faulty Sensor
The sensor may not be working properly. The PCB could be receiving incorrect signals occasionally, or the water sensor may have a permanent fault that causes the boiler to shut off repeatedly. A loose or damaged connection can calse cause the Vaillant F73 fault code persistanatly.
How to Fix a Vaillant F73 Error
An engineer can help you fix the problem if the F73 error code appears because of a boiler leak or other system issues.
A boiler leak inside can lead to water-damaged wiring. An engineer will investigate the source of the leak, then inspect the remaining parts of the boiler for damage.
An engineer can repair a leak in the boiler by flushing it or bleeding the boiler.
You might consider a new boiler if the water damage is extensive and requires many parts to be repaired or replaced.
Resetting the boiler may be necessary if the fault code displays because of an intermittent fault in your water sensor.
If this happens frequently or if the boiler is not reset, the sensor may be experiencing a permanent fault that a gas safe engineer can diagnose.
The engineer will inspect the wiring, test the water pressure sensor and repair or replace it if necessary.
How can you fix a Vaillant F73 error yourself?
This Vaillant error code will show you if there are any drips or a puddle under your boiler. You might also have heard gurgling sounds coming from the boiler.
This information is useful to give to the Gas Safe Engineer prior to them coming out. However, you shouldn’t attempt to fix the boiler yourself. It is dangerous and could lead to more expensive problems.
Sometimes a leak in the boiler could be caused by high pressure in the system. You might try to flush the radiators or towel rails in your home. However, as this involves removing the casing, boilers should only ever be bled in the presence of a Gas Safe Engineer.
Does An F73 Error Mean My Boiler Is Broken?
F73/74 is not considered minor fault. The fix should be simple and affordable as long as it is the only fault code shown (as opposed multiple codes at once). On the other hand, if your Vaillant boiler is getting old and error codes are starting to show, then it may be time to consider a new boiler.
Can You Use A Boiler with an F73 Error Code?
It is not recommended. This error can be caused by a leak. The lockout protects your Vaillant boiler parts and prevents any damage to your property. Water damage is caused when the boiler runs, which will cause more water to leak into the system.
You run the risk of further damage to your property and may need to make costly repairs.
What do I need to reset my Vaillant boiler after an F73?
The error code may be caused by a defective water sensor. If this happens occasionally, then resetting your boiler should fix the problem. If the problem persists, you should contact an engineer to fix it and possibly replace the sensor.
What is the cost of replacing a water pressure sensor?
Parts are relatively inexpensive and cost only £50. This error can be difficult to diagnose, and you may end up spending up to 2 hours labour plus additional costs if the part has to be replaced.
