The following page contains information relating to the Vaillant ecoTEC F.76 fault code, including what the F.76 fault code means, its potential causes, how this fault can be potentially fixed and if your boiler is worth repairing.
The F76 fault code explained
The F.76 fault code as explained in the the Vaillant ecoTEC manufacturers instructions states;
“Overheating protection on primary heat exchanger triggered – Cable or cable connection of fuse in the primary heat exchanger defective, or primary heat exchanger defective”
So your Vaillant boiler has a sensor built into the primary heat exchanger called a thermal fuse.
The thermal fuse is located at the very top of the primary heat exchanger and is designed to trip out if the main heat exchanger is stressed and overheated beyond a certain point.
So what causes F76 fault code?
The F.76 fault code can generally be attributed to too much heat stress being applied to the primary heat exchanger and too much stress can be caused in several ways;
(1) Poor circulation which can be attributed to a failing pump.
(2) The boiler running dry whilst operating due to issue with the pressure sensor which can result in the boiler losing pressure. A boiler running dry is often in conjunction with a faulty pressure sensor and a dripping pressure relief valve.
(3) A boiler which is not vented properly after central heating work or maintenance on boiler carried out.
How to fix F76 fault code
Unfortunately the F.76 fault code cannot 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.
As a general rule, once you see this fault code you will not be able to reset your boiler and it will not work anymore, although I have seen one or two boilers continue to work intermittently once this fault has presented itself but this is rare.
The cost to repair the F76 fault code
The bad news is that the F.76 fault generally means that the primary heat exchanger has failed and it is a very expensive component. Because of this it generally means that most Vaillant boilers are beyond economical repair once this fault presents itself.
As a general guide the F.76 fault code will usually cost somewhere between £500 and £1000 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.
Its probably worth getting a professional to confirm that this fault is most definitely a blown thermal fuse as there is a small chance it could be something like the wiring harness or printed circuit board, however it is unlikely.
Is your boiler safe to use?
On paper your boiler is probably technically not safe to use. In reality yes your boiler should be safe to use with an intermittent F.76 fault code if you have to keep resetting it, although it is extremely unlikely your boiler will reset and work at all.
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 F76 fault code
Regular maintenance is generally the key to avoiding the F.76 fault code and other problems. This can be achieved by getting your boiler serviced annually by someone who is familiar with Vaillant boilers.
Heat stress is what ultimately results in the F.76 fault code and regular boiler servicing allows for faulty parts such as the pump and pressure sensor to be diagnosed early and replaced before they can attribute to too much heat stress on the main het exchanger.
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 a good service, I have great reviews and all parts fitted come with a 12 month guarantee for piece of mind.