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 left 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.
Watched a couple of repair videos on Youtube by searching for the model number. Found out what to do in order not to get shocked by the powerful capacitor. Ordered the two switches (To be sure, I could have ordered a third switch as suggested in the videos.) Bought a tamper-proof star bit to get the cover off. Followed the directions to replace the switches. - I broke the harness and had to use some super glue, but it's all good. I should have removed the harness instead of trying to get a switch out while it was still in place. It's all back together, and the wife is happy!!
I went to LG website enter model number and was given a list of parts that need to be replaced with a percentage of which part fails the most. I order micro switch PS3522738 which arrived and PS3529293 was backordered. I installed the one that arrived. The microwave worked briefly. I reordered and waited for both switches to arrive and installed both. The microwave still doesn't work.
