I have a Hayward 400 heater that has been doing strange things since installation. It works perfectly right up to 89 degrees. At any temp over 89 it randomly locks out (display goes to "LO" ) and takes several minutes and/or several power-off resets in order to get it to fire. I've bumped up the high-limit temp and ran it in both spa and pool mode, but nothing seems to make a difference. Any ideas?