Heating has been turned off for summer but it comes on when any hot water is used either in kitchen or bathroom. Plumber has tried new pcb board and diaphram

Frances White, July 2016

Diverted valve is passing allowing the water which should be circulating around the hot water circuit to leak into the heating side.

Ian, August 2016

Manual here:

http://www.plumbcenter.co.uk/wcsstore7.00.00.549/ExtendedSitesCatalogAssetStore/images/products/AssetPush/DTP_AssetPushHighRes/std.lang.all/ti/on/Baxi_Combi105HE_Installation.pdf

Read fault analysis on Page 16

Flog through one step at a time, thinking logically.

It LOOKS like - on the basis of what I understand at the moment - that there is a problem around the bit that says "Continuity across DHW flow microswitch terminals and PCB - A5 connector terminals 5 & 6"

Read and think.

XXX, July 2016