How Often Should a Furnace Be Serviced?

The short answer is annually, before the heating season. The longer answer is that in Illinois it matters more than the national guidance implies, because our heating season runs long enough that a furnace here accumulates run hours faster than the same unit would almost anywhere south of us.

Why fall specifically

Two reasons. First, faults found in September are scheduled repairs; the same faults found in January are emergencies at emergency pricing. Second, by the second week of genuinely cold weather every HVAC company in Chicagoland is running a backlog. September and October bookings get you a calm visit with time to do it properly.

What a real tune-up includes

• Temperature rise measured across the heat exchanger and compared against the data plate spec
• Static pressure readings on the supply and return sides
• Blower motor amp draw against nameplate rating
• Full ignition sequence test — inducer, pressure switch, igniter, flame sensing, gas valve
• Burner and flame sensor cleaning
• Heat exchanger inspection
• Gas pressure verification
• Condensate drain and trap check on high-efficiency units
• Safety and limit switch testing

If a “tune-up” consists of a new filter and a visual glance, you paid for a filter change. The numbers are the point — readings drifting out of spec are how you catch a failing part before it strands you.

What you should do between visits

Change the filter every one to three months, more often with pets. Keep the area around the furnace clear. Test your carbon monoxide detectors twice a year — Illinois law requires CO alarms within 15 feet of sleeping areas in homes with fuel-burning appliances, and a furnace qualifies.

Does it void the warranty to skip it?

Frequently, yes. Most manufacturers require documented annual professional maintenance to keep the parts warranty in force. Keep the paperwork — if a heat exchanger fails in year eight, the service records are what makes the warranty claim work.