I’m not a HVAC expert, so when I say “package unit” I’m just repeating what the HVAC installer called it. The AC and the heating unit are all in one package that sits outside. There is not a separate heat/furnace that sits inside the house.
I’ll have to wait for the weekend before I’ll have enough daylight to open some panels on the unit and see if i can find out where the S1 and S2 wires go.