Replacing a Fan Motor in a KitchenAid Microwave

Bottom line: A KitchenAid microwave has more than one fan — the magnetron cooling fan, the OTR exhaust fan, and a convection fan — so the first job is identifying which one failed before ordering, since they are not interchangeable. Plan on an intermediate-to-advanced 35-55 minute repair around a mandatory capacitor discharge.

Unplug or disconnect power at breaker. DISCHARGE THE CAPACITOR before touching any internal component. The fan motors are located near the high-voltage section. Follow the complete capacitor discharge procedure even if you're "only" working on a fan.

Tools and parts#

Step by step#

1. Identify which fan failed#

The magnetron cooling fan runs whenever the oven cooks and blows air across the magnetron; if it fails, the microwave may cut out after 2-5 minutes on thermal protection or overheat the magnetron permanently. The OTR exhaust fan moves cooktop air and runs on its own speeds, while the convection fan only runs in convection mode. Match the symptom to the fan.

2. Access the interior#

Disconnect power. On OTR models have a helper support the unit while you remove the overhead mounting screws; on built-ins, disconnect the harness and slide the unit out. Remove the outer wrapper (10-14 screws around the back and sides). IMMEDIATELY DISCHARGE THE CAPACITOR using an insulated screwdriver between both capacitor terminals, then between each terminal and chassis ground.

3. Locate and remove the failed fan#

The magnetron cooling fan sits beside the finned magnetron, usually a squirrel-cage blower held by two or three screws with a 2-wire connector. The OTR exhaust fan is at the top behind the exhaust grille with a larger tangential blower. Disconnect the motor's wire connector and unbolt it.

4. Test the motor to confirm#

With the motor disconnected, measure resistance across the leads: roughly 10-60 ohms is normal, OL means an open winding, and under 3 ohms means a shorted motor — both confirm failure. Also spin the shaft by hand; it should turn freely without grinding.

5. Install the new motor#

Transfer the blower wheel to the new motor if one is not included, orient it so air flows the correct direction, and secure it on the shaft. Mount the motor in the same position, refit the original screws, and reconnect the harness. A wheel installed backward moves air the wrong way and starves the magnetron, so double-check the direction against how the old one sat before you close up.

6. Reassemble and test#

Replace the outer wrapper and remount the unit. Restore power and test the relevant fan: run the oven 30 seconds with a cup of water and listen for steady airflow from the cooling fan, press the exhaust speeds on an OTR for rising airflow, or set a convection cycle and confirm the convection fan spins.

If it still won't cool#

• Cuts out after a few minutes: the cooling fan or its thermal cutoff is still the suspect — recheck the connector and blade.
• No exhaust airflow on OTR: confirm you replaced the exhaust fan, not the cooling fan; they are separate motors.
• Fan runs after the cycle ends: that is normal, a post-cook cool-down of 3-5 minutes, not a fault.

When to call a pro#

If you are not fully comfortable with the mandatory capacitor discharge, stop here. See our microwave repair cost guide or book a same-day repair.