Replacing an Old Bathroom Exhaust Fan

Before You Start

Turn off power to the fan circuit at the breaker and confirm it's off with a non-contact voltage tester — don't rely on the wall switch alone. If the existing wiring looks damaged, ungrounded, or doesn't match what the new fan requires, stop and call a licensed electrician rather than working around it.

Step 1: Remove the Old Grille and Fan

Remove the grille cover, then disconnect the motor and fan assembly from the housing per the manufacturer's release mechanism (usually spring clips or screws). Leave the housing itself in place if it's in good condition and properly sized — many replacement fans are designed to drop into an existing housing.

Step 2: Check the Duct and Housing

Before buying a replacement, measure the existing duct diameter and housing dimensions, and check the CFM the room actually needs. If the old fan was undersized for the room, this is the moment to size up — don't just buy an identical replacement out of habit.

Step 3: Disconnect the Wiring

With power confirmed off, disconnect the wire nuts connecting the old fan to the household wiring. Note how the switch leg, neutral, and ground were connected so the new fan goes in the same way, or correctly, if the old wiring was wrong.

Step 4: Remove the Old Housing (If Replacing It)

If the housing itself needs replacing — because it's damaged, too small, or the new fan requires a different size — remove it from the joists, disconnect the duct collar, and pull it down through the ceiling opening.

Step 5: Install the New Housing and Fan

Mount the new housing to the joists, keeping it level, then reconnect the duct to the housing's outlet collar and seal the joint with foil tape or mastic. Confirm the duct still runs to a proper roof or wall termination — never into the attic — and is insulated through any unconditioned space.

Step 6: Wire the New Fan

Reconnect the wiring following the new fan's diagram, matching the switch leg, neutral, and ground exactly. If anything about the old wiring looked outdated, ungrounded, or doesn't match code, this is worth having a licensed electrician verify or correct before closing everything up.

Step 7: Reinstall the Grille and Test

Attach the new grille, restore power at the breaker, and run the fan. Check for unusual noise, confirm airflow at the exterior vent cap, and make sure the damper at the termination point is opening and closing properly.

When to Call a Professional

If the bathroom needs a new circuit, the existing wiring is outdated, or you're not confident diagnosing what's already there, a licensed electrician can complete the swap safely and make sure it passes any required inspection.