Looking for ANY help or suggestions!! Just bought a used Hot Springs Classic model F. We cleaned out the filters, filled it up with water, added chemicals, and turned the jets on. So far so good!

We then turn the dial to '3' for the heater. We can hear, what sounds like to circ pump, working. Then, within, 5 minutes the tub reset trips. We've narrowed our options down to the heater, or the high limit thermostat-but then again we could be wrong!

Any ideas or suggestions!? Thank you in advance!!