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Thermador Microwave turns on by itself

If your Thermador microwave is turning on by itself, first determine whether the vent fan is running or the microwave is actually starting a cooking cycle. On an over-the-range microwave, the vent fan may turn on automatically while you cook on the stovetop because a thermostat activates it to prevent overheating, then shuts it off after the microwave cools. If the microwave starts heating without input, check whether the touchpad responds correctly. If it does, the main control board is the most likely cause and may need replacement. A faulty interlock switch can also cause this problem, followed by a damaged or misaligned switch holder that prevents the door switches from engaging correctly. Less commonly, intermittent contact in the touchpad and control panel circuits, or in the touchpad itself, can make the microwave turn on by itself. Enter your Thermador model number to find the exact replacement part for your specific microwave. Any repair that requires removing the outer cabinet carries a serious shock hazard because the high-voltage capacitor can store lethal charge even after the microwave is unplugged. Proper capacitor discharge is required before interior work, so use a qualified technician if you are not familiar with that procedure.

01 - Thermador Microwave Main Control Board

First, make sure that the touchpad is working properly. If the touchpad is working properly, the main control board is likely at fault. If the control board is defective, replace it.
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Top Solution

02 - Microwave cooling down during stovetop cooking

Most over-the-range microwaves have a vent fan thermostat that will turn the vent fan on automatically to keep the microwave from overheating. The fan will shut off after the microwave cools back down.
Highly Likely

03 - Thermador Microwave Interlock Switch

A microwave that turns on by itself can be caused by a malfunctioning interlock switch. You can use a multimeter to test the interlock switches to determine if they are functioning appropriately and replace if necessary.
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Common

04 - Thermador Microwave Switch Holder

The microwave switch holder is the component that houses the door switches behind the control panel. If the switch holder is damaged or misaligned, the switches may not be properly engaged which could cause the microwave to turn on by itself. You will need to uninstall the control panel and inspect the switch holder to confirm it is in good condition and secured properly. Replace the switch holder with a new one if necessary.
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Common

05 - Thermador Microwave Touchpad and Control Panel

It’s possible that the touchpad and control panel button circuits are coming into contact with each other intermittently which could cause the microwave to turn on by itself. If this happens, the touchpad and control panel will need to be replaced.
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Less Common

06 - Thermador Microwave Touchpad

It’s possible that the touchpad button circuits are coming into contact with each other intermittently which could cause the microwave to turn on by itself. If this happens, the touchpad will need to be replaced.
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Less Common

Frequently Asked Questions

Why is my Thermador microwave turning on by itself?
Why does my over-the-range microwave fan turn on by itself?
How do I test the interlock switches in a Thermador microwave?
Can a bad touchpad or control board make a microwave turn on by itself?
How do I find the correct Thermador microwave part for this problem?

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