oh yessir, you are correct.
this new style thermostat only controls one unit.
it cycles something like fan lo, fan high, fan auto, cool lo, cool high, cool auto, heat lo, heat high, heat auto, then... OFF
i was watching the amp draw thru the main breaker box for each, and only got 3 dif readings.... i think i remember 0.6, 1.6, and zero. that represents lo hi off fan only. never a spike for compressor trying to hit.
i bet a lo pressure switch circuit went open, but i dont have a diagram to choose
thanks so much ill holler when monkey climbs up on top and reports!
ps the xantrax inverter reports 133 vac shore power, but i didnt gauge that.