Why does my heating only work when the hot water is on?
When central heating is selected, the valve has a microswitch that controls the boiler. If this fails, the valve moves to the heating only position, but doesn't operate the boiler, when hot water is required, because in this mode the boiler is operated by the cylinder thermostat.
Let's Get It Fixed!
HomeX virtual experts will assess your issue (for free!) and can resolve simple problems.