FCrazy

I have an (to me) odd issue with an OHH code that keeps popping back up. Temp is set to 102F. It´s a Balboa system with a 3kW heater. What I have tried: Changing filter Running without a filter All jets on Changed water When water was changed, tried to flush between filten to where the hot water comes out into the tub Verified that circ pump works (I can feel and see water coming out in the tub) After the water was changed, it did get up in temp but then ended up with OHH again. I was thinking that maybe the circ pump sometimes failed to start, but I then changed so that the circ pump was running 24/7. This worked for roughly 30 hours before another OHH. It is now fall here in Sweden, with temps around 40-45F. My current ideas are pretty much 1) still the circ pump, 2) the header or sensors therein or 3) the circuit board. Don´t know where to go from here though - I don´t want to by a part by chance. Any other tests I can do? Thanks!