Radiators work hot water doesn't

[juanpedmontoya]

I have a Biasi 24S gas combi boiler. It was working fine until tried to have a shower this morning and there was no hot water. The furnace ignites when the heating is turned on but nothing happens when the hot water tap is opened. I've tried running the tap with the heating on, the radiators heat up but the water stays cold. Temperature and pressure gauges are fine and there is definitely gas going in. I don't understand, please help!

 

[Rob]

Diverter/flow switch fault.

If it fires up on HW demand but rads get hot then its the diverter. If boiler does not repsond to hw demand then likely flow switch fault. New diaphragm/M/S required!

 

[juanpedmontoya]

Thanks Rob884. Is the diaphragm something I can replace myself? I know absolutely nothing about boilers or how they work so don't want to destroy the thing whilst trying to fix it