I'm hoping someone can offer a clue to the problem I'm having before I call a service tech.
I have a Master Spa / Down East Exeter SE Model that is about 5 years old. The spa heats up to only about 93 degrees then goes no further. The pumps run fine, no filtration problem, or so it seems. The heat indicator light on the panel flashes til it gets to 93, then just stays lit without heating any further.

I did notice that when I shut the spa off, reset the GFI and turn it back on, as it displays the voltages on the panel, it flashes 100, 113, 3 (I assume the # of pumps), 120 then goes directly into prime mode. Seems that it should also flash / check for 240 volts? Quite sure that it did before. Could this be an indication it's a GFI / wiring problem rather than a heater problem?

Thanks in advance!