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HomeRepair HelpThermador Microwave RepairThermador Microwave is sparking or arcing Repair
Thermador Microwave is sparking or arcing
When your Thermador microwave is sparking or arcing, stop using it until you identify the source. The most likely cause is a damaged, burned, or loose waveguide cover, also called a mica sheet. Replace the cover if it will not stay in place. If the microwave sparks in the cabinet area rather than inside the oven cavity, inspect the door switch, including the primary, secondary, and monitor switches, for burn marks or damage. A failed magnetron or high-voltage diode can cause microwave sparking behind the waveguide cover and may produce smoke or a burning smell. Less common causes include a burned shelf support or chipped interior paint that exposes metal. Sand damaged paint lightly and apply approved microwave touch-up paint. Do not open the outer cabinet unless you understand proper capacitor discharge procedures. The high-voltage capacitor can store a lethal charge even after the microwave is unplugged, so repairs involving the magnetron or high-voltage diode, and any interior cabinet work, may require a qualified technician. Enter your Thermador microwave model number to find the exact replacement waveguide cover, door switch, magnetron, diode, shelf support, or touch-up paint for your appliance.
01 - Thermador Microwave Waveguide Cover
The waveguide cover might be damaged and arcing or burning. If this is the case or if the cover will not stay in place, replace it with a new one.
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02 - Thermador Microwave Door Switch
If the microwave is sparking or arcing in the cabinet area, and not in the oven cavity, you will likely see smoke or there will be a burning smell. One of the appliance's door switches could have shorted and is causing the sparking or arcing. You should inspect each door switch for burn marks or damage and test the components with a multimeter to determine if any the door switches are malfunctioning.
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03 - Thermador Microwave Magnetron
If the microwave is sparking or arcing behind the waveguide cover in the oven cavity, you will likely see smoke or there will be a burning smell. The appliance's magnetron is one of the components that could be damaged and causing the sparking or arcing. Inspect the magnetron for burn marks or damage and replace if necessary.
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04 - Thermador Microwave Diode
If the microwave is sparking or arcing in the cabinet area, and not in the oven cavity, you will likely see smoke or there will be a burning smell. The appliance's diode is one of the components that could be damaged and causing the sparking or arcing. When the diode fails, it is often visibly burned out. Inspect the diode and if the diode is burned out, replace it. If inspecting the diode proves inconclusive, test it with a multimeter that uses a 9-volt battery or put a 9-volt battery in series with the diode. When the leads are reversed, the diode should only have continuity in one direction..
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05 - Thermador Microwave Shelf Support
Some microwave ovens will have cooking shelf supports on the interior walls. Inspect the shelf supports for any burnt spots or damage. If there are any burnt or damaged spots, replace with new supports as needed.
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06 - Thermador Microwave Touch-Up Paint
The paint on the interior of the microwave might be chipped. If the paint is chipped, the interior metal will be exposed, causing the microwave to spark or arc. Check the interior of the microwave for any spots where the paint has chipped away. If there are any damaged spots, gently sand the compromised area and touch them up with microwave oven interior paint.
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Frequently Asked Questions
Why is my Thermador microwave sparking inside?
What causes a microwave to spark in the cabinet area?
Can I replace a Thermador microwave waveguide cover myself?
Should I replace the magnetron or diode if my Thermador microwave is sparking?
How do I find the correct Thermador microwave waveguide cover or door switch?
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