How to Troubleshoot & Replace Lg AP4437957 / 3B73362F Microwave Door Switch

This old microwave was left with the home I purchased. It started with intermittent problems, the unit would count down on the screen, but no turntable or heat. Sometimes if I banged lightly on the door or shut the door harder, it would work. I've replaced a door microswitch before, so thought that may be the problem. I unplugged it and removed the top cover, and I could see the lower switch was burnt and some of the wire insulation was melted. I ordered the lower interlock switch from ApplicancePartsPros.com, the switch was less than $6. It was the only switch they had for it. I did remove and take apart the center (monitor) switch, and it looked new. I did some research on these switches, and the lower one is more prone to fail due to the turntable and fan power all go through these tiny contacts on the lower switch. Also, a lot of people don't know that if you open the door without stopping the operation, you send power through those contacts on that switch while opening, and causes an arc. This is what pits the contacts. It's good to remember not to interrupt the cycle by opening the door, just hit 'stop' first. I received my new microswitch pretty quick, was a little struggle to get the new one back in as you have to try and move two plastic tabs to fit it in place. Also, the wire spade connections can be difficult to remove as someone said, there is a tiny spring clip on the underside of the spade that you can press with your thumbnail, then pull the connector off the switch. I found this out by accident. I also checked the door catch surfaces for wear, there was none. While I had the cover off, I also carefully cleaned the fan motor and blade and intake screen. Also, remember to discharge the capacitor before you start working on your unit. Just take an insulated screwdriver and put the tip across the two capacitor terminals. I work slow, too detail oriented, but it went well and I'm happy to have fixed the microwave myself. Wish I could add photos. 

Replaced lower door latch switch, which was defective. Had ordered all three switches "just in case" but only the bottom one needed replacement. Thanks to the internet posts of others on this site and others, we knew what the likely culprit was and which parts to order. I love the internet and Google! Cost just $15 and a little time, and saved probably $70 - 100 over calling in a professional repair person. (Or more if we'd decided to just replace the micro.) And Appliance Parts Pros was great to deal with - shipped parts the same day, arrived two days later - perfect! Thank you! PS Repair took longer than we expected because we had to figure out how to get the old switch out - turned out that it swiveled down, after one pressed in the small piece on which it rested. Husband and wife team figured it out! 

When Microwaving food, the display panel would seem to act normal, but the typical microwave sound would be absent. No microwave action would occur. Eventually an F5 code would display. Problem was the upper door switch. Found it by opening up the cabinet, removing the display panel (1 screw and a couple of plugs) and testing all three micro switched with a meter. Two switches are for the door and one for some kind of ventilation flap. They are all in the same area. Go to YouTube to see how to test and replace these switches. This model Kennmore Elite is made by LG. 

Through a little research I determined that the primary door sensor on the microwave was bad. AppliancePartsPros got the identified parts to me quickly. I then installed the parts, the microwave worked great, and best of all I saved a couple hundreds bucks by not having to buy a new microwave/pizza oven. 

Our oven wouldn't cook but the fan and light would come on with the door open. After reading many forum posts on the internet I determined that either 1 or more of the interlock switches had failed. I couldn't tell from testing them so I ordered all three switches from Appliance Pros. The switches were about $15 with shipping and all right to my door and arrived in 3 days. I was able to install them and now the oven works as it should. I was unable to tell which switch(es) were bad from testing them with an ohm meter. They all had continuity when they should have and none when they shouldn't. I just threw them away. The oven has been fixed now for several days and we haven't had any more problems with it. It is nice to have a venue like Appliance Pros to look all this up and be able to find a solution. This oven wasn't cheap and it's only about 2 years old. It should last many years. Thanks 

Search Internet and the the door switches were likely the problem. Took it apart and tested the switches and found two of them to be bad. Ordered them from appliance parts pro and received them the very next day using standard delivery. ~$15 total and fixed. 

You tube and other sites said it was one of the door switches, called micro switches...so I went to AppliancePartsPros as I always do, and ordered ALL switches and one fuse for less than $21...then I used You tube to figure out how to remove the control panel to expose the switches...I used a magnifying glass and bright light to match new to old so as to confuse switches as they all three looked alike..installed, while unplugged of course, in 30 mins and had my $500 micro working and saved a bundle...the bad micro switch has a spring loaded orange or green button that gets pushed in..it should always click back out..mine was stuck "in", so if you can see/test the button by pressing it and it isn't stuck in, then may be ok...but for price, i replaced all switches with new...be careful pulling off wire clips, pry with flat screwdriver and watch that the metal clip slides back inside the plastic covering before you re-plug it onto switch..use mag glasses and good lighting and fine point needle nose to do work. 

Took the MW apart via removing the three screws on the sides and the screws on the back(some nut had put tamper proof torex with a pin in the center to stop me from removing them, vice grips did the job). Pretty easy fix when found out there were three micro switches and used ohm meter to find defective switch problem. 

Replaced the microwave door switches. There are 3 of them, one at the top and 2 at the bottom of where the door latches into the main body of the microwave. You have to remove the upper vent guide (it pulls out) to expose the single Philips head screw that holds the right-side panel in place. Once removed, the right-side panel lifts out. I took several digital pictures of all the wire connections on the circuit board so I could unplug them all and get the panel out of the way. The door switches are in a plastic piece that is held in place with 2 Philips head screws. Remove those and pull the wire connectors off of each switch so you can get the entire plastic piece out. The switches are held in place with a plastic post and other molded plastic pieces. Be careful not to break the pieces holding the switches. I actually broke one on the bottom switch so I had to use gorilla glue to hold the new switch in place. The total time would have taken less than 15 minutes to complete. 

Initially the microwave would cook normally and then when you open the door it would turn back on. This would happen intermittently. After doing that for a while, it stopped cooking entirely. The timer would count down but no cooking. I had to also buy security torx bits to get into the microwave. I found them at my local hardware store. After taking off the case I shorted the HV capacitor with pliers. There were no sparks. The replacement was easy. They just disconnect and pop out. The bottom switch tested bad.