Panasonic Model NN-T994SF runs for approximately 30 seconds and stops. The unit still has power to the front panel and can be restarted (for an additional approximate 30 second interval before it stops again) and does not appear to be cooking at all.

I have intermittent cooking problems

Many over-the-range microwave ovens suffer from intermittent problems caused by excessive moisture from the range/stove entering the microwave cabinet and collecting on the circuitry. Often the problem is with one or two simple connections that may need tightening or soldering. But, to repair these components, the microwave cabinet needs to be opened. So we recommend that you seek the assistance of a qualified appliance repair technician.
I have intermittent cooking problems Many over-the-range microwave ovens suffer from intermittent problems caused by excessive moisture from the range/stove entering the microwave cabinet and collecting on the circuitry. Often the problem is with one or two simple connections that may need tightening or soldering. But, to repair these components, the microwave cabinet needs to be opened. So we recommend that you seek the assistance of a qualified appliance repair technician.

You can also download your manual below to see if troubleshooting helps.

http://www.retrevo.com/s/Panasonic-NN-P9...
You can also download your manual below to see if troubleshooting helps.
http://www.retrevo.com/s/Panasonic-NN-P994-Microwaves-review-manual/id/2915ci161/t/1-2/

It doesn't work at all

If your microwave oven doesn't seem to work at all, check these:

Fuses
Door switch




Fuses

Usually, when your microwave oven doesn't work it all, the internal fuse (thermal fuse) is blown. This fuse protects both you and the oven. When it blows, you need to have a qualified appliance repair technician replace it.





Door switch

If the fuse isn't the problem, check the door hooks and the door-release button. When these are broken, the door switch doesn't activate, so the oven can't work.





It sounds normal, but there's no heat

When the microwave sounds okay, but there's no heat, one of the internal door switches, the high voltage circuitry, or the circuit board may have a problem. To resolve this problem, you need the assistance of a qualified appliance repair technician.
It doesn't work at all If your microwave oven doesn't seem to work at all, check these:

Fuses
Door switch
Fuses Usually, when your microwave oven doesn't work it all, the internal fuse (thermal fuse) is blown. This fuse protects both you and the oven. When it blows, you need to have a qualified appliance repair technician replace it.

Door switch If the fuse isn't the problem, check the door hooks and the door-release button. When these are broken, the door switch doesn't activate, so the oven can't work.

It sounds normal, but there's no heat When the microwave sounds okay, but there's no heat, one of the internal door switches, the high voltage circuitry, or the circuit board may have a problem. To resolve this problem, you need the assistance of a qualified appliance repair technician.