Chicago Furnace Tune-Up Checklist Before Winter

Published: April 15, 2026 · By SAVA HVAC & Appliance Repair

Chicago winters regularly see temperatures below 0°F. When your furnace fails in January, you're looking at burst pipes, emergency service calls, and hotel bills. A simple fall tune-up — done in September or October, before you need the heat — can prevent almost all of it. Here's a room-by-room checklist to get your furnace ready before winter hits.

1. Replace the Air Filter

A dirty air filter is the #1 cause of reduced furnace efficiency and overheating. If your filter looks gray and clogged, replace it. Most 1-inch filters should be replaced every 1–3 months during heating season. High-efficiency 4-inch filters can last 6–12 months. When in doubt, replace it — filters are cheap, furnace repairs are not.

2. Check and Test Your Thermostat

Before you need it for real, switch your thermostat from cooling to heating mode and set it 5 degrees above room temperature. Does the furnace start within 1–2 minutes? Does it reach the set temperature? If the furnace doesn't respond, start with fresh batteries. If it still doesn't start, the problem may be the thermostat or the furnace control board.

3. Inspect the Pilot Light or Igniter

On older furnaces with a standing pilot light, the flame should be steady and blue. A yellow or flickering flame can mean incomplete combustion — a safety concern. On modern furnaces with electronic ignition, listen for a clicking sound when the furnace starts. No click, no heat — that's a failed igniter, one of the most common furnace repairs we see in fall.

4. Look for Cracks in the Heat Exchanger (Call a Pro for This One)

The heat exchanger separates combustion gases from your home's air. A cracked heat exchanger can allow carbon monoxide to enter your living space — which is why it's the most serious furnace issue we find during inspections. You cannot reliably inspect a heat exchanger yourself. This is the step to call a technician for.

5. Test Your Carbon Monoxide Detectors

Before heating season starts, press the test button on every CO detector in your home. Replace batteries if needed. CO detectors should be replaced entirely every 5–7 years. If your detector is expired or missing from your furnace room or sleeping areas, replace it before you fire up the heat.

6. Check the Blower Motor and All Vents

Walk through your home and make sure every heating vent is open and unobstructed. Blocked vents cause pressure buildup and reduce efficiency. Then listen to the blower motor when the furnace runs — it should be smooth and quiet. A loud humming or rattling blower is a sign the motor is struggling and may need service.

When to Call a Pro

Some of this checklist you can do yourself. But if your furnace doesn't start, makes strange sounds, smells like gas, or hasn't been serviced in over 2 years — call before winter, not during it.