Paint damaged in side microwave oven

This is because the coating inside the oven or the wave guide has been damaged and microwaves are hitting bare metal and causing sparks. Take the light bulb out of it and when it is dark, put a glass of water in it and turn it on. If you can see the sparks then you know what needs to be repaired. You can buy microwave oven paint. It is special paint though, you cannot just use any paint. If you cannot see sparks then the area that is damaged is inside the unit and it should be taken in for repairs. If you don't fix it, it will blow out the magnetron and you will be looking at a new oven.

Your description is a little vague. I am assuming that you are saying that the inside of the unit has black scorching marks near the area that the interior light bulb is housed. If that is the case then the coating on the inside of the microware is compromised. This is usually caused from food particles getting stuck the inside or it has become scratched. When this happens, the microwave will continue to spark in that area, This will result in further black marks and it will cause the entire unit to fail at its most expensive part, sooner. You can take care of this issue by cleaning the interior very well and then paint the inside again with microwave oven paint. It has to be special paint.

see the troubleshooting section and follow the steps and fix it.
God bless you

Waveguide Cover

If the microwave is sparking or arcing the waveguide cover might be damaged and shorting out. Try removing the waveguide cover and see if the problem goes away. If there are any damaged spots in the microwave ceiling or sidewalls, repair them and paint them with microwave oven paint. Replace the waveguide cover if it is burnt or if it will not stay in place.

Microwave Oven Paint

If the microwave is sparking or arcing on the side walls the paint might have chipped causing pitting in the metal oven wall. Use microwave safe paint to touch up any bare metal spots.

Rack Support

If the microwave is sparking or arcing near one of the rack supports, remove the support, repaint any bare metal, install a new support.

follow this steps and fix it. God bless you

Waveguide Cover

If the microwave is sparking or arcing the waveguide cover might be damaged and shorting out. Try removing the waveguide cover and see if the problem goes away. If there are any damaged spots in the microwave ceiling or sidewalls, repair them and paint them with microwave oven paint. Replace the waveguide cover if it is burnt or if it will not stay in place.

Microwave Oven Paint

If the microwave is sparking or arcing on the side walls the paint might have chipped causing pitting in the metal oven wall. Use microwave safe paint to touch up any bare metal spots.

Rack Support

If the microwave is sparking or arcing near one of the rack supports, remove the support, repaint any bare metal, install a new support.

see this steps and fix it. 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.
If your 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.

see the guide for test the magenetron and another component.

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.
If your 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.

see the next steps and follow with common sense: God bless you
Microwave is arcing 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.
If your 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 bel

2 things cause sparks.... a damaged Waveguide RF window or bare metal inside the cooking area. If you note bare metal you can sand and paint it with an appliance enamel paint. (no lead paint!) Just make sure to only sand the area your painting as any sanding scuffs not painted will hasten a repeat performance of the sparking routine. The RF will bounce off bare metal and cause the sparking. Once PROPERLY painted it no longer sparks.

If it is coming from the area of the Waveguide RF window... Make sure the window is replaced before next use.

Thanks for choosing FixYa,
Kelly

Check to see if there is any rust or cracks in the coating that came from the factory. Some microwaves use metal underneath an epoxy type coating and if it is exposed, it can cause an arc from the microwave generator. If there are any defects in the surface, it can be sanded down and you can purchase a can of interior microwave paint and put a coat of paint over the defective area. Also look for any exposed metal in the area of the sparks, there should no metal exsposed anywhere, if it is, cover it with the paint. hope this helps.

it is not safe to use this, DO NOT USE, repalace immediately, no need to repaint