My Panasonic microwave is over ten years old, but works great. The problem is it has a small rust spot at the bottom of the door and sparks when turned on. What can I do? It has a metal cabinet and isn't used much - rust is mostly on the cabinet, but a little on the door. Lowell

Could be grime. If that is rust then maybe there is too much humidity at the location of the microwave. Could also be old age.

If there is spark please do not switch on unless you have confirmed the fault. It is possible that the Magnetron is leaking and sparking to the ground. As you have mentioned it was stored, it is quite possible that insect can get into the oven and create soft spots. When you switch on these will create a short and make the voltage jump and in the long run damage the magnetron.
So Remove cover after disconnecting , check for dirt/moisture in the cabin, if so wipe clean and dry, check the magnetron and area clean and use an jet air to clean off.
Now switch the microwave power on and use a cup of water to test.
If you notice any sparks shut off as the magnetron or the main HT capacitor can be faulty. Replace with same type. If not check the waveguides within the cabin for food particles that can burn and spark, check for rust that can corrode and spark when the ceramic paint has worn out.
If there is heating without any issues, you can use the microwave safely

Click on replacing waveguides: http://www.espares.co.uk/advice/microwave/a/5/1146/how-to-replace-a-microwave-guide-cover.html

If there is spark please do not switch on unless you have confirmed the fault. It is possible that the Magnetron is leaking and sparking to the ground. As you have mentioned it was stored, it is quite possible that insect can get into the oven and create soft spots. When you switch on these will create a short and make the voltage jump and in the long run damage the magnetron.
So Remove cover after disconnecting , check for dirt/moisture in the cabin, if so wipe clean and dry, check the magnetron and area clean and use an jet air to clean off.
Now switch the microwave power on and use a cup of water to test.
If you notice any sparks shut off as the magnetron or the main HT capacitor can be faulty. Replace with same type. If not check the waveguides within the cabin for food particles that can burn and spark, check for rust that can corrode and spark when the ceramic paint has worn out.
If there is heating without any issues, you can use the microwave safely

Click this link:Waveguide

We have a Panasonic Inverter microwave. Door became difficult to close and had to slam it hard while holding themicrowave to keep it from moving. When opening the door did not pop open but did unlatch. I ordered a new door lever from Panasonic. When got part I removed case from microwave and lever was okay. I then removed the perimeter strip on the inside of the door. With a screwdriver I stretched the spring at the bottom that keeps the door latches pulled downward. Spring still worked just not as stiff. Put perimeter piece back on the door and replaced housing (which I didn't need to remove in the first place), and then put a small drop of vegetable oil on the cams where the door latches hit when closing door. Viola, door opens and closed as new. Problem solved. Diagnosis: over time the latch tension spring hardens and gets too stiff. P.S.: I had several similar springs as backup in case I screwed up the original one.

Yes you can paint it.. Begin by removing the rust with either a wire brush or a thick paste product called naval jelly. Then prime the area and finally paint it with appliance paint, abailable in a spray can at most hardware stores in the color of your appliance.

This is just okay but if you're quite doubtful you may bring this to any appliance service center for repaint

To replace the inner part of the latch is actually quite easy. Remove the glass tray from inside, then unplug the unit. Take to a flat surface and stand on edge so that the door will open flat. On the inside is a plastic trim that is just clipped on. Pop this off carefully and you will now see the assembly you need to replace. Note where the spring is anchored to the door before taking it apart. Put a small amount of lubricant on the guide pins of the new catch (petroleum jelly works great).

Moisture accumulation can sometimes be caused if the cooling fan is not running properly or if the vents in the back are blocked or there is not enough free space around the sides and back of the microwave.

One thing that helps is to keep the door open a few minutes after using it and to wipe down the inside after use.

If the cavity metal of the oven is chipped or charred, it will have to be sanded smooth and clean and dried thoroughly.

Then you can apply some high-temperature appliance paint, available from places like Wal-Mart, Lowe's or Builder's Square.

We're happy to help you with free advice and we'd appreciate your thoughtful rating of our answer.

just use sand paper to clean the rust then use some high temperature paint (sold in tins) eg spray paint but it must be labeled high temperature and spray 2 to 3 coats . your microwave should be safe again

Hello SusanWargin,
In my opinion ( and that is all it is).. I have always stood by the old litmus test whereby : if the cost to repair is close to or exceeds the cost to replace, then replacement makes sense. From the description you've presented and considering your micro is 12 years old, there is a reasonable chance that other components ( magnetron, transformer et al) will begin failing and end up costing more and more. So.. I would support your decision to replace with a new one. (again, this is only my opinion but I say this with sincerety and some experience with these appliances) ...Good Luck deciding..