HVAC in North Dakota is the heating-season trade, full stop. No heat, weak heat, or a blower that runs while the rooms stay cold are the calls that matter. Furnaces in basements, boilers on older main streets, and propane burners on farmsteads are not the same machine. Say which one is in the house. A high-efficiency unit that will not run because the condensate froze is a different visit from a heat exchanger you should not trust. Do not blend them.
Intake and exhaust pipes ice. Terminations buried in a drift or aimed into the wind will shut the burner down on the night you need it. Condensate lines that were pitched like an afterthought freeze and trip the equipment. Filters pasted shut and a thermostat in a hallway that lies will make a good burner look dead. Ask what was ruled out. Rooms over a garage and ducts in a freezing attic are load problems, not thermostat personality.
If you smell combustion trouble, stop using the equipment until someone has seen the flue and the heat exchanger. That is not a comfort complaint. A cracked exchanger is a reason to shut the unit off. Short cycling, a yellow flame where it should not be, or a rollout mark belongs in the first sentence. Have the town ready and say whether any heat is moving at all. A space heater story is not a repair.
Replacement should happen before the deep part of the season if you can choose, because living through a no-heat day here is not a small inconvenience. Ask whether the load was calculated for this house, including the wind and the glass, or copied from the old label. Matched equipment and ducts that actually connect are the scope. Efficiency labels are a test comparison. They are not a promise about the fuel you will burn in January. Say if you are on propane, because running out is its own emergency.
Say heat, the town, and whether the burner is dead, noisy, or simply losing to the windward rooms. Mention ice on the pipes outside or a filter you can no longer see through. If the house is cold now, say that first. The heating season does not accept a wait-and-see. Call the number on this page.