Fan keeps going after Microwave stops

"The exhaust fan thermostat is usually the failed component. When it senses heat it turns on the exhaust fan. If you are cooking on the cooktop, it can sense the heat and the fan won't turn off until the thermostat cools.

On several models of microwaves the thermostat is super sensitive, causing the exhaust to run longer than needed. Replacing the thermostat didn't help much. Adding a washer under the thermostat allowed air to move around it, keeping it cooler, thus, the fan didn't run as long.

It is also common for this thermostat to fail causing the fan to constantly run.

The thermostat is a round disk with 2 terminals. It is a simple bimetal that warps to make or break contact. It is an inexpensive part $20-$50.

It is NOT an easy part to get to. The microwave has to be completely uninstalled and placed on a sturdy table. The cabinet needs to be removed. Then discharge the capacitor. If you don't know how to properly discharge a capacitor, I would suggest having it repaired by a certified/qualified technician.

==UNPLUGGED == A CAPACITOR CAN HOLD UP TO 4,000 VOLTS.

THAT CAN AND WILL KILL YOU...DEAD"

"I know that this may sound like I’m joking, but I am not doing so. We just now experienced this issue with our microwave. After trying several solutions, I firmly (but gently) hit the edge of the door of the microwave with the heel of my hand below the control panel, and that worked to turn it off. As I mentioned above, this is something that just now happened, so I am NOT going to try to recreate the scenario.

The microwave is a GE - Model number is: JNM3151RF1SS"

"The microwave fan will sometimes come on when your not using the microwave. It does this when your cooking something on the cooktop below the microwave. Boiling potatoes or pasta or something that is creating steam is usually the culprit.

The thermostat senses the heat and turns the fan on.

You should have the microwave checked out by a qualified technician. A survey test should be performed by technician every time it is serviced.

Remember, the capacitor inside a microwave can hold 4,000-6,000 volts even after its been unplug for days and even weeks.

This means that a microwave doesn’t need to be plugged in to KILL you."

I found if I place a small fan so it blows across the stove top it prevents it from happening or shortens the duration if it does.

This just started happening to my GE Profile Microwave today. I tapped the cabinet portion with the heel of my hand near the top on the handle side and it stopped. Thanks to everyone who continues to answer this thread.

Omg that worked. I moderately smacked the face of the control panel and the vent stopped.