What could be causing the hot water side of my Ideal Isar combi to not work, when the central heating side is ok?

E Spink, March 2007

check wether the diverter valve (grey plastic box with a lever in the middle)is moving as the heads have a tendancy to fail.
when selected for hot water by drawing off the hot tap the valve should be seen to move, if it doesnt the system is stuck in the heating position and will not provide hot water.

watknig, March 2007