A boiler that still heats the radiators but has no hot water at the taps is a different fault from one that has stopped altogether. Both need a Gas Safe registered engineer if the appliance is a gas boiler. Neither is a reason to open the case.
Heating on, hot water off
On a combination boiler, that pattern often points to the hot-water side of the appliance — a sensor, a diverter, a plate heat exchanger or a related control fault. On a system with a cylinder, the fault may be on the cylinder controls or valves rather than the boiler itself.
The useful information to give when you call is:
- whether the radiators are still heating
- whether any taps are producing hot water
- any fault code on the display
- whether the problem started suddenly or faded over days
Nothing at all
If there is no heating and no hot water, start with the obvious household checks only: the thermostat is asking for heat, the programmer is on, and the boiler has electrical power. If the appliance is in lockout or will not fire, stop there.
Do not keep resetting it. Do not touch gas isolators unless you have been shown the emergency meter control and you need it for a suspected leak — in which case you should already be calling 0800 111 999.
Pressure and other system symptoms
Low pressure can stop a boiler running. Repeated repressurising is a symptom. Cold radiators with a boiler that claims to be firing can be a circulation problem rather than a hot-water part.
See signs your boiler needs repair if several of these are happening together.
What happens on a visit
We diagnose the appliance and the way hot water is produced in that house. Sometimes the right job is a repair. Sometimes the boiler is the wrong type for how the house is used now, and the conversation moves to replacement.