HVAC Maintenance Calendar: What to Do Every Month, Season, and Year

Monthly Tasks (Year-Round)

Check the air filter. Hold it up to the light — if you cannot see light through it, replace it. Most 1-inch filters need replacement every 1–3 months. 4-inch media filters last 6–12 months.
Check the area around the outdoor unit. Clear any debris, leaves, or vegetation within 2 feet of the condenser. Do not stack items against it.
Check the condensate drain line. If your air conditioner is running, verify the drain line is draining. A clogged drain line causes water damage and system shutdowns.

Spring (March–April): AC Startup

Schedule a professional AC tune-up before the cooling season. Chicago summers arrive fast — do not wait until June.
Remove the outdoor condenser cover if you installed one for winter.
Clear debris from around the outdoor unit after winter.
Test the AC before you need it — turn it on and verify it cools. If it does not cool properly, call for service before the heat arrives.
Check and replace the air filter.
Check the condensate drain line and clean it if needed (a cup of diluted bleach poured down the drain prevents algae growth).

Summer (June–August): Cooling Season

Check the air filter monthly — summer operation with AC running continuously loads filters faster.
Keep the outdoor unit clear of vegetation. Grass and weeds grow fast in Chicago summers.
Monitor your energy bills. A sudden increase in cooling costs can indicate a refrigerant leak or dirty coil.
If you have a whole-home humidifier, turn it off for the summer or set the humidistat to its lowest setting.

Fall (September–October): Furnace Startup

Schedule a professional furnace tune-up. This is the most important maintenance task of the year for Chicago homeowners. A furnace that fails in January is an emergency — a fall tune-up prevents that.
Replace the air filter before the heating season begins.
Test the furnace before you need it — turn it on and verify it heats. If it does not fire, call for service while the weather is still mild.
Test all carbon monoxide detectors. Replace batteries. Replace detectors older than 7 years.
If you have a whole-home humidifier, replace the water panel and set the humidistat for winter operation.
Check the furnace flue pipe for obstructions (bird nests, debris).

Winter (November–February): Heating Season

Check the air filter monthly — heating season with the furnace running continuously loads filters faster.
Keep the area around the furnace clear. Do not store combustibles near the furnace.
Check the condensate drain on high-efficiency furnaces — it can freeze in very cold weather if the drain line runs through an unheated space.
Monitor the humidifier — verify it is adding moisture and the water panel is not clogged.
If you have a boiler, check the pressure gauge monthly. Normal operating pressure is 12–25 PSI for hot water systems.

Annual Professional Service

Two professional service visits per year are the standard recommendation for Chicago homes:

Fall furnace tune-up: Burner inspection and cleaning, heat exchanger inspection, controls check, safety device testing, flue inspection, filter replacement.
Spring AC tune-up: Coil cleaning, refrigerant check, electrical inspection, capacitor test, drain line cleaning, filter replacement.

D's Air & Heating provides furnace and AC tune-up service throughout Chicago and the surrounding suburbs. Contact us to schedule your seasonal maintenance.