I recently purchased a used 2003 Cal Spa, Fiesta Atlantis, 450 gallon. Everything looks great and all seems installed properly. When I first started it it was on Economy Heating Mode and heated to 80 degrees and held this temperature. I reset it to standard heat mode and the heater and heater light would not go on. I reset the breaker a couple of times and the heater and light did go on and heated to 100 degrees. I tried to increase the heat to 102 and the heater shut off. The next day the heater light would not go back on even when I would reset the breaker. It is clean and has a new filter. All the jets and the pump seem to be working well. Any advise? Please help. Thanks!