Vaillant ecotec Plus 831 F75 repair Rotherham

This was a little repair I did last week on a Vaillant ECOTEC Plus 831 Combination boiler in Rotherham, which had an intermittent F.75 fault. This fault happened mainly when the heating was on.

When the Customer called he was certain that the expansion vessel was the cause of the fault, and thought this would probably