HVAC in Sioux Falls spends its life in wind that makes one side of the house cold and the returns dusty. A furnace can be healthy while the rooms facing the open edge never match the hallway thermostat. That is infiltration and duct reality, not a slogan about winter. Say whether the equipment will not run or the windward rooms will not catch up. Corner lots in new subdivisions and older houses under trees both do this, with different dust and different ducts.
Look at side-wall intake and exhaust pipes. A gust on that wall ices terminations and upsets draft. Filters cake after a dry blow across bare lots. A condenser on an open pad collects the twigs and seed the wind carried, and then the house will not cool when the summer heat shows up. Ask what was checked before parts are named: filter, coil, ducts, and whether the outdoor unit is buried in debris. A closed-off return can imitate a dead compressor.
High-efficiency condensate lines and attic ducts are the quiet failures. Ducts leaking into a vented attic give the heat to the wind. If you smell combustion trouble or a heat exchanger is in question, stop and have it seen. Do not season the conversation with a promise about the bill. Labels compare a test procedure. An exposed Sioux Falls lot is not the test lab. Matched equipment is a different scope from a new outdoor unit on an old coil.
Replacement should account for the windward glass and the open fetch, not only the square footage on a listing. Additions and bonus rooms over garages never keep up if the ducts were an afterthought. Say if a bedroom on the north or west is the complaint. Say if the problem started after a blow filled the outdoor unit with debris. Those are different visits, and the first sentence should pick one.
Say heat or cooling, the neighborhood, and whether the failure is the machine or the side of the house the wind hits. Mention ice on a termination or a filter you just changed that is already black. If the house is uncomfortable now, say so. Call the number on this page.