My 7 year old Vaillant boiler originally broke down in December and displayed the error code F76. My nearest Vaillant recommended engineer in Guildford came, pressed the reset button and it started again and ran for approx 3 weeks. Since then it has ceased to work with progressively less running time in between and now will only start and run for 5 mins before displaying the error code. The Boiler Engineer undertook a service on one of their five emergency call out calls,but only tested the expansion vessel(empty) and checked the circuitry on their last visit and seem to think that the fault lies with a fuse in the heat exchanger, however it is generally assumed that the boiler would not start at all if this was the case, so I am now at a loss as what my next course of action should be. I understand that Vaillant have a fixed replacement part cost for replacing faulty parts. The Boiler Engineer is saying that the fuse alone cannot be replaced and that I need to replace the whole heat exchanger and the expansion vessel. Please let me know what the cost would be and how I should go about it.
The F.76 fault code on the EcoTEC Plus 637 model is a safety protection shut-off when the primary heat exchanger overheats. The three causes of this fault is a defective primary heat exchanger, primary heat exchanger fuse cable connector is damaged or the primary heat exchanger cable is damaged.