Hi Colin.
I'm no expert, so don't take a pinch of what I say to be of any expert advise, however, i do like to think that i'm analytically minded
If the water is only getting to 34 and you can hear the heater boiling, i'd suggest there may be a flow problem. Water doesn't boil at 34.
If it's boiling inside the heater chamber, then surely it can only be a flow problem.