MA780M LG - Instructions

Turned the microwave on its side. (Recommend turning it on its top. i had to fish the wire connection back to the center after it dropped away from the motor.) There is a spot under the rotation motor where an access port was stamped in the tin but not cut out. Used the small side cutter to complete the cut where tin had been left between holes. I unplugged the wires, removed the old motor by removing one screw, and installed the new one by reusing the same screw. The motor must have a reduction gear inside the case. The motor coil tested good, about 128 ohms, but it acted like there was a stripped gear inside. I wasn't interested enough to try to open the motor and confirm.

Had to go to the garage and get a small sheet metal screw to close the new trap door.

The "new" motor had scratches on it, made me wonder if it was really new, but it works fine and will probably outlast me.

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.

Removed some cosmetic panels. Removed the assembly with micro switches. Examined the faulty switch by checking the clicking action of switch. Two others were ok by this method. Replaced the switch with new one. Works fine so far. Thanks to web site and YouTube videos.

There were two hard parts for me to work through.

The first was breaking off the two screws that need a special head screwdriver to remove. None of my special special head screwdrivers worked (I have a few), so I used a hammer to force them off.

The second hardest part for me was finding the correct replacement bulb on-line. My Amana Microwave is a combo Microwave/Convection type, and it's a strange little bulb - almost tube like.

Once I did find the right bulb on this PartSelect.com website it was a breeze. The part was delivered in just a couple of days (even during this Covid-19 pandemic). Once I had the replacement bulb in hand it barely took 5 minutes to install.

Thanks PartSelect!!

1. Order correct light bulb for unit and have it with you before removing old lightbulb.
My Microwave is built into cabinet.
2. Disconnect power (Either turn breaker off or unplug unit from wall)
3. Remove face cover on cabinet. (4 Phillips head screws)
I was able to reach in the opening in the cabinet and unplug from the wall.
4. Remove Phillip head screws holding microwave in cabinet.
5. Remove microwave from cabinet.
6. Remove Phillip head screws and torx screws holding outside cover on the back of unit and the side (1 on right side) and then remove cover.
Light bulb is on the top front right side.
7. Remove 1 philip head screw holding light bulb and unplug quick connector wires.
8. Plug quick connector into new light bulb same way it came out and place new light bulb in place and put the 1 philips head screw holding it back in place.
9. Put cover back on and all the screws. Temporary plug the unit in to test light bulb works before securing it back into cabinet.
10. Reverse order 5,4,Plug unit in wall before putting the face back on.
Done.

Required that i remove the built in frame and mounting. Required tamper proof socket to remove housing. I removed the old bulb and simply replaced and reverse installed the cabinet.

Take cover off microwave. Check door switches to determine which one was faulty.Remove and replace faulty switch.

i unplugged the unit,unscrewed the outer shell so that all the wiring and internal components were visible.starting at the first of three micro switches i removed the slip on terminals installed the alligator clips too the wires so the switch would now be bypassed.i made sure the wires and clips were not touching anything plugged unit in and it worked.i then installed the new switch and closed up the outer shell

I looked up my problem on the internet and found a very helpful video. Microwave on video was different brand but the internals and methods were very much the same. The video made it simple and easy to fix. Found the replacement switch on the LG parts site and ordered. Two different switch types. One with red switch, the other green. Part was $7.28. Saved a bundle in service costs. Here is the repair video.

https://www.youtube.com/watch?reload=9&v=_AglBJoHgDs

tested cap. with ohm meter which showed a short. A new HV cap., a fuse and it is working fine again.

Problem was due to a faulty door switch. Replaced with a new switch and the microwave now works fine! Only thing that was tricky was that LG uses the hex screws with a peg in the middle to keep the microwave cover on. Had to use a small screwdriver and pliers (on the screwdriver) to unscrew the screws.

Easy, and the microwave still doesn't work.

Take off cover then the bottom. Transformer is on the bottom plate and wires won't let it come all the way off, too many wires to pull off so will have to position the bottom plate so you can get to the motor. Remove 1 screw on motor and remove motor. Install new motor connect wires replace bottom plate, replace cover. All done (hope & pray it works ok) mine worked perfect. Hope this helps.

Unplug.Take off the external cowling from the back of the unit by removing the torx security screws. Tip: instead use a thin screwdriver blade to unscrew the torx screws, or knock out the center pins of these screws. Remove the bottom panel. The replacement motor is attached with one phillips screw, re-attach wires to motor - polarity doesn't matter. Re-assemble and you're finished.

Overall repair quite simple. Removed screws from the sides and rear of the microwave, then removed cover. Next, removed only the screws to separate the bottom cover. Removed the one screw in the AC Synchronous motor to remove the motor (had to use small screwdriver through a vent slot in the bottom to remove the screw). Unplugged and removed motor. Installation is the reverse of removal. Note: on the back of my appliance were 4 torx screws with a tamperproof pin in the center. I used the rotary tool to grind out the pins so I could use a regular torx bit instead of ordering specialty bits.