I'm experiencing the same situation with my tub - no heat on low, pump runs all the time. I wanted to test to see if it was the pressure switch or the element - i doubted it was the element, since i just filled the tub less than a week ago and it got nice and too hot. last night when i got home from work, i kicked the jets on to see if i could get the tub to heat up - within an hour it went from 95 to 102 - so that indicates to me that the element is in fine shape (i thought it was as i pulled it out to replace the high limit switch 5 days ago) - so i believe my problem is the pressure switch. i ordered a new one for the tub and also a new element - i figure while i have the whole heater assembly out, i might as well replace the element since i've got new everything else LOL. i hope this resolves the issue i'm seeing.

I have a new element on order, waiting to arrive any day. Still not sure thats the problem but I have traced everything back to the element. The problem with the pump running all the time was a bad contact relay. That problem is sovled.