Originally Posted by Complete-Heat
Solid boiler but the ecotech pro is prone to a sticking pump which i think the op has.
Wirring noise is either air stuck in pump or bearings on the way out.
Good thing about Vaillants is they often diagnose themselves if you know how to get the 'S' codes and 'D' diagnostic codes....
Yep, fault codes are pretty good on these. Did get F28 the other day on another one (usually no gas etc, etc), condense had frozen and backed right up into boiler. Defrosted, stripped down, dried, refitted ....working now...you live and learn, lol. Still recommend these and fitted about 300, 3/300 needed attention in last 5 yrs so not bad,