I don't think I'm going to try this myself. Found out that if the heating is on when the tap is running then the water cones out hot and the burner isn't clicking on and off. I don't know if this can help anymore with identifying the issue
Seen this issue or similar issue before accross the forums read through multiple posts on different websites but just want alittle more information from whats going on with mine.
CH Circuit working fine
DHW - Water gets warm then goes cold then warm then cold.
No erorr code lights on...