see this next steps. God bless you
If you see arcing or sparking inside a
microwave, turn unit off immediately. Arcing can be caused by having
something metal in the oven cavity touching a side, an oven shelf is
touching the side of the cavity, an oven shelf support has broken,
microwave waveguide, or bad magnetron.
If your microwave has a
shelf in it, and you do not use it, keep it out. If one of the shelf
supports breaks or comes out, the microwave will arc where the support
was. You will have to sand the spot down, paint with appliance paint
and re-install support. If the shelf shifts on the support and touches
the side it will arc.
Your magnetron waveguide will either come
out of the top, or side of the oven cavity. Some will have a stirrer in
it(mostly top waveguides) with a panel over, or just a cardboard type
cover over it. Over time, the stirrer cover can become warped from the
heat which will expose the stirrer's metal shaft which will then cause
sparking. These covers and stirrers come in a kit and can be replaced
from inside the oven cavity.
Your cover over a side waveguide is
coated with a substance on it, and overtime this coating can come off
from the heat and moisture in the microwave. These waveguide covers are
very easy to replace from inside the oven cavity. Touch up any paint
that may have chipped or come off because of the arcing.
waveguide cover and/or stirrer are all OK, then the spark is coming from
your magnetron. The antenna on your magnetrom has overheated and
burned, sending the microwaves out at the wrong angle. If you catch
this microwave oven repair early enough, you can usually get by with
just replacing the magnetron. If the arcing has caused servere damage
inside the waveguide, you will need a new microwave. Waveguides are not
replaceable and most you can barely see into them, let alone sand and
re-paint. In this case of microwave oven repair, when you remove the
magnetron, you will see the burned antenna, or your magnetron will fail
the test below.