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John, restaurant equipment technician
Category: Appliance
Satisfied Customers: 2136
Experience:  25+ years experience. I'm now employed by a commercial cooking equipment service company
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My built-in Jenn-Air microwave, about 5 years old, suddenly

Resolved Question:

My built-in Jenn-Air microwave, about 5 years old, suddenly stopped microwaving. That is, the power is on, my commands register on the display, the light comes on, the carousel turns, and it beeps when the time is up. Only problem is: no microwaves were generated so food is as cold as it was when it went in.

I might be able to fix this myself by buying a spare part (or two, or a dozen), but I don't know what mechanism needs to be replaced. Is there any way to know which one or ones is/are broken? Then, is it relatively simple to follow the schematic to replace the bad part/parts?

Model #: jmc9158bas

I would go here to order the part(s):

In the end, is it easier to replace it? If so, how do I find the exact same size unit (it's built-in)?

Thank you,

Submitted: 5 years ago.
Category: Appliance
Expert:  John replied 5 years ago.

Does the oven have its usual humming sound, when it's running?

Customer: replied 5 years ago.

Hi John:


Yes, it sounds the same including the hum, but maybe a little "rougher", like a car engine running rough. It's very subtle though - I never put my ear that close to it when it worked :)

Expert:  John replied 5 years ago.
It's most likely the magnetron that's failed. It's the part that produces the microwaves. The power supply circuit that makes it radiate microwaves has 4,000 volts, and it's best to have it repaired by a professional service person. The part is about $150.00. It will be better to repair it, if possible, as it's difficult to find a new one that has the same measurements as yours.
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