Why won't Microwave door stay shut?

Jo. you may have to remove the hole cover, to access inner latch mechanism, where you can manipulate the latch with long screw driver.*** before attempting this, unplug microwave for an hour***
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Microwave Door Won Open

Hello Scott Noble - If I was in your position, I personally will recommend consulting a certified technician first for an accurate diagnosis. Depending on what part(s) is damaged from the door, the microwave could possibly have faulty switches, door switches, or latch which only a professional can repair.

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.

I have the same problem. Is the light still on inside the microwave? Mine is on and the microwave thinks the door is not shut. I took the top off of the microwave and the latch needs to push down on a switch once shut. The latch was reaching the switch, but I think some spring in the door, pushing the latches down, has broken since it reaches the switch when closed but there isn't any downward force to flip the switch.
I am trying to figure out how to repair the latch but if your light is on when you "shut" the door, you may have the same problem.

If the door will not stay closed it is the spring inside door, or the small plastic piece that holds the spring which is attached to the $80.00 piece called outer door.
To fix it, it is EASY and you do not have to even take the inside cover all the way off. Just remove the three sides of cover by gently slipping a plastic putty knife around rim to release the clips. Then attach the spring to the small hole below where the plastic piece used to be, which is located in the metal on the glass frame piece, use tweezers, hold the other end of spring as you place spring onto plastic door latch and set into place!
Snap the inside cover back on and YAY! FINI!

Most likely there is a part missing from the door latch mechanism that you need. This probably broke off when the handle failed. It would be a tab or wedge shaped piece of plastic that strikes the door switch and pushes the switch closed when the door is completely shut. You will need to find that piece and glue it back on or get a new handle assembly from Samsung.

If it's not heating at all, the magnetron is to blame.

take it toy your local repair shop and have the door latch replaced

Yes. One of your door switches is not working. It could be an alignment issue or a faulty switch. There are actually 3 switches in the door latch area.
Eric

I answered this personally via e-mail (and I do not mind peopke writing me personally). I think you may have a broken tab which holds the door latch head spring in place.