Problem with ideal isar H - 2 flashing

[help me please]

Hi we are having problem again with ideal isar.When the boiler is cold we can run hot water. When the central heating is on and we put the hot tap on the heating stops working and no water is being heated and H2 starts flashing.Then we have to wait for it to cool down before we can use either the heating or hot water not both together. Please help. thanks

 

[gas4you]

It will be the return thermistor or the pcb.

Remove and check the resistance values of the thermistor to whats in the installation manual. If these are ok it points to the pcb.

 

[help me please]

Thanks i forgot to say when we have a shower or use a lot of hot what we have to wait for it to cool down before we can use it again.