James B Rocky Hill , NJ November 17, 2017 Appliance: LG Microwave Oven LMV1813ST Microwave shut off without usual beep at end of cycle no power to unit even though plugged in. Replace Thermostat on top of cavity. The thermostat is attached via 2 bending sheet metal tabs. Ours blew because the two wires connected to thermostat shorted, connectors melted. The short was caused by buildup of grease under thermal wire cover, shorting both leads. The unit is used heavily. This is the first thermostat to go. I had to replace wire connectors that connected to thermostat as well since the connectors were melted as well. Helpful hint. The grease build up was probably caused by obstructed air flow from the stove top through the exhaust vent. BE CAREFUL. The exhaust vent on the back of the unit has a flap that opens up when the fan is on. There are tabs on the top of the vent frame that are bent down, so that when the flap opens it is blocked from opening 100%, and instead only opens about %40. This obstructed flow, in my opinion, reduces air flow rate, which allows exhaust to back up and collect, as well as thermostat and unit to overheat. Solution: Bend the tabs up on the back of the exhaust vent to allow the door to open fully. Double check if there is another vent on your wall to the exterior, and make sure it fully opens as well. Read More... 8 People found this story helpful Do-It-Yourself Rating: Repair Time Estimate: 30-60 minutes Tools: Screwdrivers