The following page contains information relating to the Vaillant ecoTEC F.74 fault code, including what the F.74 fault code means, its potential causes, how this fault can be potentially fixed and if your boiler is worth repairing.
The F74 fault code explained
The F.74 fault code as explained in the the Vaillant ecoTEC manufacturers instructions states;
“Water pressure sensor signal out of range (too high) – Cable to water pressure sensor has a short-circuit at 5 V / 24 V or internal fault in water pressure sensor”
So your Vaillant ecoTEC boiler has a component called a pressure sensor. The pressure sensor’s job is to determine if there is enough pressure in the system for the boiler to work safely, and to determine if the pump is working sufficiently for the boiler to go onto the next part of the ignition sequence.
The F.74 fault code means that the printed circuit board is detecting a short circuit or excessively high voltage back from the pressure sensor.
So what causes F74 fault code?
The F.74 fault code can generally be attributed to one of the following issues;
(1) A faulty pressure sensor.
(2) The pressure sensor being exposed to too much pressure because of too much pressure in the boiler.
(3) A faulty wiring harness.
(4) Corroded connections on wiring harness, usually caused by a leaking pressure sensor.
(5) A faulty printed circuit board.
How to fix F74 fault code
Unfortunately the F.74 fault code cannot generally be fixed by an end user. If you are not qualified to work on your boiler then the only option is to reset your boiler and hope it will work until you can get it looked at by a professional.
If you have have overfilled your system by mistake you could try bleeding a radiator to relive the system of excess pressure and this may solve this problem.
The cost to repair the F74 fault code
The good news is that the F.74 fault generally means that your Vaillant boiler is worth repairing and you probably do not need a new boiler!
As a general guide the F.74 fault code will usually cost somewhere between £100 and £200 to repair depending on the model of your Vaillant boiler and its age and assuming you don’t have any other issues with your boiler.
In my experience this fault is quite rare and one you will probably not experience very often. This fault will usually be caused by a faulty sensor or too much pressure in the system.
Is your boiler safe to use?
Yes your boiler should be safe to use with an intermittent F.74 fault code if you have to keep resetting it.
My advice would be to get this fault code investigated at your earliest convenience by a suitable Gas Safe registered heating industry professional who is familiar with Vaillant boilers as it is unlikely to keep working intermittently indefinitely.
How to prevent the F74 fault code
Regular maintenance is generally the key to avoiding the F.74 fault code and other problems. This can be achieved by getting your boiler serviced annually by someone who is familiar with Vaillant boilers.
Regular boiler servicing of your Vaillant boiler allows for faulty parts such as a leaking or faulty pressure sensor to be diagnosed early and replaced as part of preventative maintenance and prevent any issues in the future.
Vaillant Repair Service South Yorkshire
I offer maintenance services for most Vaillant boilers and I cover a large part of South Yorkshire including most of Sheffield, Rotherham and Barnsley.
My services include include emergency call outs and routine boiler servicing.
I am Gas Safe registered, fully insured, carry plenty of spares for most of the Vaillant ecoTEC range of boilers and generally repair most boilers with one visit.
I provide an excellent service, I have great reviews and all parts fitted come with a 12 month guarantee for piece of mind.