MSER0990S (CSTELGA) LG Miscellaneous - Overview

After watching a few youtube videos, I used a phillips SD to take controll pannel off to access the switches that sense when microwave door is closed. Swapped out all 3 switched and mocrowave works like new. $20 fix (shipping included)

Unplug the unit before servicing. Need phillips screwdriver. Open door. Use step ladder to access and remove 2 small screws from top of the room air diffuser at top of unit. Slide diffuser slightly to the left to align the diffuser's plastic tab on the left side to rotate toward you. (The wires for the front control panel are at the far l ... Read more eft side of this difuser, but difuser is slotted for easy removal). Once the difuser is removed you will see 1 screw at the top that secures the pannel cover on the left side of the unit. Remove screw and slide this panel slightly up and out. This exposes the plastic frame that holds the upper and lower door switches. To locate the door switches and observe how they work, close and open the door and watch the door (bayonets) open and close the micro switches. Do the (red) buttons on top of the switches move up and down when the door bayonets push and release? If the buttons do not "pop" up when opened the switch is defective. The switch frame is secured with 2 screws. Remove screws and rotate the unit out for easy access to the micro switch(s). The internal (spring?) on my unit that is suposed to allow the red (visible) button on top of the switch to "pop" up when the door is opened was broken. Carefully pry the switch outward while being careful to lift the plastic holder-piece that holds the switch in place. Be careful, there is a small pin on the frame, so rotate the switch OUT toward you while lifting (carefully) the plastic holder-piece (you will see it on top of the switch). You can use an ohm meter to test the continuity of the switches. But if the buttons don't "pop" they are defective. Replace switch and reassemble.

Fun and easy fix for my kids.

The countdown timer was working but no "cooking" happening. Did not hear the familiar sound of the heating part working.

Determined it might be some simple switches for under $15 dollars. Bought one of each. They allow the microwave to turn on/activate by signaling that the door is prop ... Read more erly latched. My wife noticed that it was failing and then failed over the course of about a day. Several times where it worked, then did not work. The timer was counting down one time and then when she opened the door the microwave heating component turned on. Guess it had activated the switch as she was opening the door.

Procedure to repair
- Unplug
- Remove two screws on front top - allows you to remove the vent. Realized there was a charcoal filter there that I had never replaced so ordered that after the fix.
- Remove two screws to pull off the front right panel (area where your microwave buttons are) One at the top under the before mentioned vent and one under the microwave on the far right corner.
- Have someone hold the panel because wiring is to short to place it on a ledge while connected or take a picture and remove connections. I simply held it while my daughter undid the micro switches.
- Carefully remove micro switches. There were two "orange" button ones so I chose the top one to replace along with the green button one that I had ordered, so I simply pulled an orange from the bottom and a green from the top latch area. You may have remove the part that holds the switches since it was a little tough with the wires in the way and not knowing how the switches stay put.
- plug in new switches and place in the brackets that hold them in place
- reverse everything you did.
Viola - a working microwave vs purchasing a brand new for several hundred dollars or having to call in a technician.I love that my young kids did this project with me and we actually got it running. Don't like to have to throw away more items at the landfill.

Semi-Handy Man