Ideal isar H2 fault code

[proelitegas]

Hello people just had a call from A customer who is getting H2 fault code on the display and complaining of intermittent hot water..I know many of you out there hate this model and would reccomend axing it to death lol but they are everywhere I go..any advice would be appreciated I'm thinking maybe a thermistor problem as CH is fine

 

[Mbear]

I tend not to think ntc's are at fault it they are dry as the Isar primary Ntc's are.

Maybe a choked plate. Difficult one