Why does it get to hot and shuts down before end of timer and no ding, food stays cold

The part of the oven called the "magnetron" (this part is what creates/generates the microwave energy that heats the food or liquid) is burned out, the cost to repair is more this part is more than the cost to replace with the cost of Microwaves so depressed by the stagnant economy.

The most likely problem is the magnetron that heats the food, the other less likely is the high voltage transformer that energizes the magnetron. To replace either part with labor would be as much if not more than a brand new microwave oven.

The door switches are slightly out of alignment. If you run the microwave and shift the door up or down, the micro might begin working..
The control panel must be removed and the door switches adjusted. I would not suggest you doing this yourself, as it may affect the microwave leakage through the door gap.

Mine also does the same thing however I only need to lift the door upwards slightly (after it's closed) and it engages the High Voltage Transformer, thus working as normal.

Once you know that, you can get it to work every time. I beleive the clips on the door don't properly stop latch in correctly and the safety feature keep the microwave from acutally turning truly "ON".

The magnetron (the part that heats the food) may be bad or the circuitry to the magnetron may have burned out. Basically my advice is that if you have no electrical expertise, it isn't worth fixing. The magnetron if bad, costs almost as much as a new microwave. If you open it up (make sure it has been unplugged for a few hours and don't seen any obvious burnt parts, then most likely the magnetron is done and a new microwave is the way to go.

Let me know how this works out for you.

Benjamin

The evaporator coil behind the cover on the back wall inside the freezer will ice up under normal conditions. Every 8 to 10 hours for around 20 minutes the defrost timer (or in most newer models the electronic adaptive defrost control) will turn the defrost heater on to melt the built up ice. There is a defrost thermostat which prevents the heater from overheating the freezer by breaking the heater circuit when the temp reaches close to 32 degrees F. The entire cooling system shuts off during the defrost cycle and starts back when the timer advances through the cycle.

If this ice is not melted it will continue to build up until the air can’t flow over the coil to circulate the cold air through the freezer and into the fridge. The temperature change in the fridge is usually noticed first followed by the freezer.

If the defrost thermostat is bad it can prevent the heater from coming on OR it won’t turn the heater off when it gets too warm. It is clamped to the evaporator coil at the top to sense the temp. If it appears to be misshapen it is bad.
With an ohm meter it should show continuity when cold and none when warm.
You can also bypass the thermostat to see if the heater comes on then. If it does then you know the thermostat is bad and needs replaced.

The defrost heater is located on the evaporator. It is in a tube which is at the bottom and can also go up the sides of the evaporator. On some types you can see a burnt spot if it’s bad. With an ohm meter it should show continuity from end to end when disconnected from the wiring in the freezer. You can also test the wiring for voltage when it’s in the defrost mode.

If you have a defrost timer you can test it. It can be located under the fridge behind the kick panel on the front. Some are in the fridge with the controls at the top. You can turn the defrost timer till it clicks and everything shuts down. The heater should now come on. If it does, replace the timer because that means the timer is not running. If it doesn't, check the heater and defrost thermostat. Turn the timer again till everything starts back up to end the defrost cycle.

If you have an adaptive defrost control instead of a timer, replace it if the heater and thermostat test good. It is located in the fridge with the controls in some models and on the back in others.

May be a shorted metal stirrer fan bearing located within the wave guide that feeds microwaves into the cooking area. If the oven is run without a proper load (water, or food), the voltage of the microwaves increase considerably causing things to arc-over inside the wave guide. You usually can't see the stirrer bearing short as it occurs internally.

One of the following has failed -

Magnetron
Transformer
Diode
Capacitor
Fuse (but these don't blow for no reason.).

These can be purchased and replaced, being careful to re-assemble all covers and housings exactly as disassembled. Same thing happened to my in-laws several years back.
You can find P/N's for each of the components listed above on the components themselves, or from an appliance website.
The only component that is testable is the transformer. Fuses can be replaced (see note above), but the diode and magnetron are not testable without special equipment. They are cheap enough anyway, when compared to the cost of replacing the whole unit.

But by all means, do not repair if you feel you cannot reassemble exactly as the unit came apart. Your dealing with invisible microwave radiation, and that can hurt you. An improperly reassembled unit is dangerous.

check the magnetron might need to be replaced