How do I fix heating on Isar HE30 combi boiler?

if you have a dripping tap, even a slight drip, this will cause the boiler pre-heat to activate and you get no heating. make sure no taps are dripping first off, if still showing 'd' the turn off the cold water supply to the boiler, if you get heating after that then you may have a leak somewhere on the hot water pipework. i know it sounds daft that a drip will cause this, but this boiler uses the hot water temperature sensor to detect if a tap is running and even the slightest amount of water running causes this.

Ian
April 2012

Might sound a bit obvious but have you checked the water pressure gauge is 1.5 bar usually underneath these boiler small round gauge showing pressure

Bal
April 2012