Hi, I have an Ariston DIA 20/24 MMFI CE boiler that has stopped supplying hot water. The central heating is working well but as soon as a hot water tap is turned on the burner shuts off. The 'Fault Finding' procedure in the service manual asks to check the 'flow switch on the main circuit'. I've checked the resistance of the reed switch with no hot water demand and the resistance is 0 ohm. When a tap is turned on the resistance changes to 1 ohm. I assume that this proves that the flow switch is OK. Is this correct? The other reasons listed in the service manual are (1) the PCB and (2) the 'temperature probes'. Ive changed the PCB and it had no affect on the hot water supply. I've found what i believe to be one temperature probe but i don't know how they work and therefore how to test if it is OK. If anyone can help with the overall problem of no hot water, or just on the temperature probe identification & understanding i would appreciate the help. Chris
