HVAC in Milwaukee is a heating season measured in months, not in a cold week. Equipment starts when the lake chills and is still running while milder places have quit. Steam and hot water still carry a lot of duplexes and flats. Later forced air in bungalows leaks heat through ducts that were an afterthought. A dead unit is not an inconvenience here. Wait, and the pipes are what fail next.
Report banging pipes, a cold radiator, water on the floor, or a smell at the draft hood. Do not summarize that as the heat being a little off. Lake wind changes chimney draft in these masonry flues, and a spill is the first sentence, with people moved to fresh air. Condensate lines on newer furnaces freeze outside and shut the unit down mid-season. Say if that already happened once.
Summer is short, humid, and hard on a side-yard condenser. Cottonwood fluff finishes the outdoor coil. Say if this is a summer complaint so it is not treated like a winter no-heat call. Window units in brick openings drip, rattle, and disappear in the fall when the boiler takes back the house. Filters clog faster when the fan runs for months. A closed return in a bungalow will starve a furnace that otherwise tests fine.
Name steam, hot water, or forced air, and how long it has already run this season. A tune in early fall is not the same ask as no heat on a lake-effect night. Radiator covers and painted valves belong in the description if one room is cold. Replacement is not a vent, and a vent is not a new boiler. If only one duplex unit is cold, say so first.
Lead with no heat, a leaking boiler, a frozen condensate line, or a side-yard condenser that died. Say which floor stayed warm. Name tonight if the house is already cold. Milwaukee's heating season does not pause while you describe the thermostat. Call the number on this page.