I have a KitchenAid wall oven microwave combo unit. After having some cabinets redone the oven was reinstalled but was wired incorrectly. The 240V circuit going to the oven is only 3 wire (so two hot and one neutral/ground), but the oven wiring is 4 wire. The oven neutral was connected to one of the hot wires (it had been Sharpied black but that had worn off), both oven hots (black and red) were connected to the other hot wire, and the oven ground was connected to the ground wire.

When the breaker was flipped, the oven started making a buzzing sound and we could smell something burning. I'm assuming the neutral for the 120V circuitry being connected to a hot was not good for said circuitry. I'm also assuming the two 120V circuits making up the 240V circuit being in phase was not good either.

I rewired the oven to have the red and black wires each connected to a hot, and the neutral and ground wires both connected to the circuit ground/neutral. At this point, no buzzing sound but also nothing on the control panel.

I replaced a decent sized fuse that was accessible from a side panel on the oven that sounded like it had been spent when I shook it, but that didn't fix anything.

How can I fix this? Where should I start testing to try and determine what part(s) were compromised?

  • Hello, and welcome to Home Improvement. Unfortunately, any answer to this question will be a matter of opinion. Aug 15, 2020 at 21:52
  • Yeah, that’s true. I guess ultimately I’m just looking for some thoughts/ideas/suggestions. Perhaps I should rephrase the question.
    – Bryan
    Aug 15, 2020 at 21:55
  • I would imagine your control/circuit boards are toast . The fuse was probably for the microwave so that might have been saved.
    – JACK
    Aug 15, 2020 at 22:40
  • I found a 2nd fuse that’s the fast acting microwave fuse. It’s ceramic so I won’t be able to test if it’s blown until I get an ohm meter. I agree the control/circuit boards are probably toast but none of them exhibit any burnt components. From how things are wired I would also think a particular transformer could be burnt out but it doesn’t exhibit any burn marks either.
    – Bryan
    Aug 16, 2020 at 0:30
  • 1
    Well, the marking was defective. In fact the wiring was improper. It has never been legal to use /2+gnd for a 3-wire range connection. 3-wire range connections were only legal with /3nognd or SE cable to allow stocks of those to run out. After that, /3+gnd became the only acceptable cable. Aug 16, 2020 at 21:13


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