This whole thread started on a red herring,
As already mentioned it's probably a thermister.
Tony it's a useless flow switch design i changed 10 a week. But never for this fault, it always fails the other way, doesn't fire the boiler for hot water.
The diverter valve in the other hand is 10 times more reliable than the flow switch.
The pcb's are bulet proof.
But though you will need a flow switch one day and you might need one now for other reasons it isn't your fault this time.
Unles that is you have a leak on a hot pipe or a seriously running bath tap combined with a leaching diverter valve. Not unheard of but much less likely as a cause than the thermister.
If you asked for my money on the table I wouldn't put it on the pcb or the flow switch. It would go on the running oldfashioned bath mixer or a thermister.
The simple test even the diy guy can perform is isolate the cold feed under the boiler.
As already mentioned it's probably a thermister.
Tony it's a useless flow switch design i changed 10 a week. But never for this fault, it always fails the other way, doesn't fire the boiler for hot water.
The diverter valve in the other hand is 10 times more reliable than the flow switch.
The pcb's are bulet proof.
But though you will need a flow switch one day and you might need one now for other reasons it isn't your fault this time.
Unles that is you have a leak on a hot pipe or a seriously running bath tap combined with a leaching diverter valve. Not unheard of but much less likely as a cause than the thermister.
If you asked for my money on the table I wouldn't put it on the pcb or the flow switch. It would go on the running oldfashioned bath mixer or a thermister.
The simple test even the diy guy can perform is isolate the cold feed under the boiler.