Hello my name is Barry and I will be assisting you.
Unplug the microwave. Avoid touching anything inside that microwave other than the board and the touch panel. The capacitor in there stores voltage and it does store 1000's of volts and you would not want to get into that.
Disconnect the touch pad (arrowed blue) from the control board (arrowed green). If the fan and light then stays on when you open and close the door replace the control board, part number W10127098.
If it does not then stay lit replace the touch pad part number DE34-00233G.
The U. S. Consumer Product Safety Commission (CPSC) warns against do-it-yourself repairs of microwave ovens. Each year, on average, four people die from electrocution trying to repair their microwave ovens. Microwave ovens use high voltage which makes it particularly hazardous for consumers to remove the cover and touch electrical parts. The possibility for electrical shock from a microwave oven still exists even after the oven is disconnected from the power source. Should certain internal devices fail, even unplugged ovens can cause serious injury.
The Commission strongly recommends that consumers have professionals repair microwave ovens because electrical appliances can be hazardous if consumers expose live electrical parts.
Removing the cover of your microwave oven and touching an electrical part can kill you.
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