LG Microwave won't turn off

Often that is due to accumulated grease on the door open button and the opening in the plastic control panel frame in which it moves.

See these links before proceeding:
http://031d26d.namesecurehost.com/mwd/safety.txt
http://031d26d.namesecurehost.com/mwd/disassembly.txt

You can find links to helpful exploded view diagrams and part ordering help for most brands here.

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Take the cover off end take a look how the hinges are mounted on it, If they are bolted on they can be readjusted, He man, Use your brain .

see this causes and fix it. God bless you
Open Lever If the microwave door won't open the open lever might be broken. This part can be replaced separately.

Door Spring If the microwave door won't open the door spring may have broken. The door spring is located inside the door and keeps downward pressure on the door hook.

Door Latch If the microwave door won't open the door latch might be broken. The door latch is inside the microwave. The door hook, which is part of the door, engages with the latch to keep the door closed during operation. If the door latch or actuator breaks the door may not open.

Door Hook If the microwave door won't open the door hook might not be releasing properly. The door hook is installed inside the door and normally releases when the door is opened. The hook is made of plastic and will break over time. When this happens it will need to be replaced, it can't be repaired.

Button Spring If the microwave door won't open the button spring might be broken internally. The button spring can be replaced.
Button If the microwave door won't open the button might be broken internally. The button can be replaced.

Handle Actuator If the microwave door won't open the handle actuator might be broken. This is a plastic part which can become brittle over time. This part is connected between the door button and the door latch assembly.

The service manuals are at our site here and here.

You can order parts from the Sears Parts Direct Web site or Encompass here.

We're happy to help you with free advice and we'd appreciate your thoughtful rating of our answer.

Mine did this too. Also, at times when I would shut the door, the whole keypad would go dark and the clock would have to be reset. There were also times when I would push Start and it would do nothing. I'd have to unplug it so it would reset itself.
I used a screwdriver and forced the door open. Mine is about 2 years old and it's now dead. Biggest piece of junk I've purchased in years. Really ticked me off, no more LG products for me. I had a Toshiba that lasted me 22 years and the only thing that went bad on it was the light stopped working and the fan cover fell off.

That sounds like the control pad or control unit has failed. I would call an engineer.

Thinkind about it, if you open the door, the light is on and you canset time etc but no start function.
Check/replace the door interlock switches as I think there will be a faulty one or the small internal fuse has blown if it has two fuses.
Hope this helps.

open the control push boton and clean it one of the boton stoct.

This problem normaly happens when the door is not closed properly for a long time and flashing and buzzing starts to give user a indication for same. Allthough it is not risky as microwave oven has safty door switches wich does not allow oven to operate while door is open. Take care and close the door properly before you leave kitchen..

Time for a service call. Should not turn on by itself at any cause. Circuit board is my guess. May be cheaper/easier to get new microwave. My first one lasted about 15 yrs--and the circuit board (touchpad) died. Bought new microwave oven.