Microwave starts running on it's own

clear and re set cooking cycle

If all the settings work and the door closes ok . why throw it out ?. It may not be quite as efficient power wise as a brand new one. the few cents extra to run it against the price of a new one, I would stay with old faithful.

Possibly a bad oven temp sensor. If the uinit doesnt read a temperature it will shut down to prevent a fire or over heating. The temp sensor is a thermister A temperature variable resistor that changes value as the temp changes. so If the main board doesnt get a response within a vertain resistance range it shuts things down. Sometimes since those parts are in the actual cooking area and subject to the heat and steam from cooking they can rust and break, or just get old and break. Or slam the door and break, you get the idea!!

Sounds like stuck relay contacts. Magnetrons need a high voltage source which is controlled by a micro to relay and then from relay to voltage source. Even the turntable works via a relay.

My immediate reaction would be to cut your losses and buy a new unit as sooner or later you will run into a part that is no longer available.

That could very well be an issue with the power supply. The chances on a relay failing on the DPDT switch side are very rare. Something is not telling the relay to close.

Hello,

Check the turntable guide to make sure it is lined up properly and that there is no debris caught in it. You may need to re-align or clean your turntable guide.

Cleaning and realigning a turntable guide;

Remove your glass turntable cooking tray from your microwave. Gently wash with warm soapy water to remove any debris. Next remove the turntable guide and clean it in the same manner, with warm soapy water. Pay particular attention to the turntable rollers. There could be spilled food particles caught in the rollers, hindering the rollers' movement. Also, gently cleanse the internal cavity of your microwave, paying special attention to the area below the turntable.

With the internal cavity, turntable, and turntable guide completely clean and dry, return the parts to your microwave. First place the turntable guide on the bottom of the microwave. There should be a circular groove in the bottom of the microwave cavity keeping the turntable guide in place. Follow the guide with the turntable cooking tray. Carefully place the glass tray over the turntable guide and onto the drive bushing. The drive bushing should fit neatly into the grooves on the bottom of your glass cooking tray. It may take some adjusting before the tray will sit properly onto the drive bushing.

Test your microwave after this thorough cleaning and realigning in order to determine whether this has solved your problem. DO NOT run your microwave with nothing in it.

CAUTION: Your microwave oven is capable of giving you a serious electrical shock, even when it is unplugged. We strongly suggest you seek the assistance of an appliance repair technician when conducting any microwave oven repair.

Also, Examine the plastic drive bushing the turntable tray sits on. It may have become worn, or even may have split in two;

Drive bushing replacement

Inspect the plastic drive bushing located below your microwave oven's turntable tray. There may be some debris blocking the tray's range of motion. Clean away any blockage you find, and then test your microwave to see if this has cleared up the problem. DO NOT run your microwave with nothing in it.

However, if upon your inspection, you notice that the plastic drive bushing below the turntable tray is worn and/or broken, you will need to have the bushing replaced. Consult with a certified and experienced appliance repair technician. Replacing a drive bushing is a lengthy and involved process that the average layman should not perform.

Good luck.....

If it stops after 7 seconds, it has a problem with the inverter.

If the digital programmer circuit / controller does not get a feedback signal from the inverter for a period of 3 seconds, the controller will stop the cook cycle.

It may be a loose connection in the wiring between the inverter, magnetron, and/or control board, or maybe one of those components has failed.

Due to the lethal voltages used and produced in inverters, I do not recommend that an inexperienced person work on these.

You can find an authorized Panasonic servicer here.

In Canada, you can find an authorized Panasonic servicer here.
If you prefer to replace the inverter yourself, you can find links to helpful exploded view diagrams and part ordering help here.

I recommend that you bookmark that link to your favorites.We're happy to help you with free advice and we'd appreciate your thoughtful rating of our answer.

this would be the digital control board that would need to be replaced

The oven may not be seated properly. check the bushes at the bottom.