The usual suspect: the diverter valve
On a combi boiler, a diverter valve decides whether hot water goes to your taps or your radiators. When it sticks, the boiler can end up favouring one over the other — classically, plenty of hot water but no heating. A sticking or worn diverter valve is one of the most common combi faults we replace.
Thermostat, programmer and valves
If the heating won’t come on, it’s worth ruling out the simple things first: the programmer set correctly, the thermostat calling for heat, and the batteries in a wireless stat. Beyond that, a motorised valve that’s failed can stop hot water reaching the radiators even though the boiler’s working fine.
Heating fine but no hot water
The reverse — radiators warm, taps cold — again often comes back to the diverter valve, or on some systems a failed hot-water element or a scaled-up heat exchanger. It’s worth a proper diagnosis rather than guesswork, as the fix depends on which.
One working and the other not? It’s usually a single part — and we’d rather diagnose it properly than have you replace a boiler that doesn’t need it. Gas Safe engineers across South Manchester and Cheshire.
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