Diverter valve needs changing
Definetley diverter valve as its only opening to one way.
Most likely to be the motor or the valve ceased up. Thats if its a combi boiler
Ex British gas engineer
If it's a cumbi it could be the HW section of the diverter valve, if its a full system Check the hot water Diverter.
If you have a combi boiler,than it could be the diverter valve. But if its a different system than it might be several reasons.
Brian, I wish I knew the kind of system you had! Is it Combi? Regular boiler or system boiler......with tanks??
Nick shares his story of finding local tradespeople in his new area.