Do I Need to Do Anything to My Furnace Before Switching to AC?

Written By Ashly Hughes

Should I Turn My Furnace Off Completely? No.
Your furnace still runs the blower motor during cooling season. It helps circulate air throughout your home.
Do not:

  • Shut off furnace power

  • Flip furnace breaker

  • Close supply vents


What Should I Do Before Cooling Season?
1. Replace the Air FilterYour furnace filter works year-round — including during AC season.
2. Check Humidity LevelsMinnesota winters are dry. Spring humidity rises quickly.
Ideal indoor humidity:

  • 30–50%

If humidity climbs too fast, your AC may feel less effective.

Should I Close Vents in Unused Rooms? No.
Closing vents increases pressure in the duct system and can reduce efficiency.

What About My Humidifier?
If you have a whole-home humidifier:

  • Turn it off

  • Shut water supply valve

  • Set control to summer mode

Leaving it on can create excess indoor moisture.

How Do I Know My System Is Ready? Ask:

  • Is airflow strong?

  • Does thermostat respond correctly?

  • Does outdoor unit start smoothly?

  • Is there unusual noise?

If yes — you’re ready for spring.

Ashly Hughes
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