Valiant Ecotech Plus 637 - Error F76

[techweb]

A couple of weeks ago my Valiant Ecotech Plus 637 displayed Error F76. Boiler is 13 years old; serviced annually.

I power cycled the boiler and it operated for ~10 days before hitting the same error again; I once again power cycled the boiler and it was in operation for ~24 hours before displaying the F76 once again. I power cycled it and it ran for just a few hours before hitting F76 for a third time.

I have now power cycled and done a P0 test and the boiler is back in operation for the last couple of hours.

Clearly this isn’t the thermal fuse and I would be suspect if it is wiring given the fact that reset clears this condition. I have come up with a potential trigger however… Whilst the central heating side of the boiler has been untouched; I have over the last couple of weeks turned the water off for a period and drained some hot water from the megaflow. Once was as we were away for several days (I did turn off the H/W heating whilst away). On our return we hit this error 4 days later. Yesterday, the water was turned off and some H/W drained to replace a shower.

 

[cjg]

its an overheat ntc on the boiler that will throw that fault, try turning temp. down to 50, running boiler for a day or two make sure your air bleed is open on pump, see how that goes.

 

[techweb]

So, I lowered the radiator temp to ~55 degrees and ever since the boiler has been stable. It must be temperature related but clearly my boiler must have an underlying fault. I will have a plumber check the wiring etc but it will get me by for now. I'll tend to it ahead of the winter.