Do you know which sensor you replaced? The one with the smaller threads is the one that is probably the culprit. I think it's the middle plug on the control box.
i have replaced both of them now high limit and i believe the flow sensor. on the power board I am not getting any power past the transformer but it ohms out ok i now supect the transform is not getting the signal to kick on to drive the relays leet me know if i am wrong in this line of thinking?
thanks
Jason