KItchenAid microwave KHMS1850S: interlock switches replaced, but fuse keeps blowing

I would change the interlock switch under the door catch. They do intermittant things like this when contaminated.

Pulled up a schematic on this will try and help the first pic looks as though you removed the secondary switch the bottom one if so that is the wrong switch it should be a normally open switch that one is normally closed this switch goes up top on the other side of the primary switch the one with 3 terminals, look at the second pic the switch with 3 terminals that red wire in the wrong spot the skinny orange goes there the switch I just told you to put up top the red goes to one terminal the white and brown middle form the 3 terminal goes to the other terminal, the blue/white and blue go to the bottom switch this is a normally open switch if you don't know how to read a switch look at the switch look at com follow the line to where it stops if it is NO=normally open, NC=normally closed your primary switch is in the right spot you want the switch next to it to be NC and the bottom switch NO it blew the 20 amp fuse once you correct the switches and wiring and put in a new fuse if you have no power then it blew past the fuse and burnt out the filter board happens some times about 60 bucks let me know if this helps

see this causes and fix it .God bless you
f the microwave will not work at all, make sure power is on at the outlet and test the electrical cord. Test the fuse and replace it if it is faulty. Also check the door to make sure it closes properly. Test and, if needed, replace the fan. If the oven doesn't cook or cooks only intermittently but the display is on, check the door interlock switch, the thermal cutout (see the Applaince Controls Fix-It Guide), and the fan, replacing parts that don't pass the test.
If the oven keeps blowing fuses, check for a faulty door interlock or monitor switch.

HELLO.

the problem your are experiencing with your microwave oven is a failed interlock switch.
Be careful when closing your microwave door. Slamming the door too hard is one of the main reasons that the interlock switch is damaged.

Slamming the microwave door shut can easily blow the microwave fuse, but they can also blow due to problems with the interlock switches.
A microwave oven will not function until the fuse is replaced.

Instruction on how to replace fuse on microwave.

1. Unplug the microwave from the electrical outlet to prevent electrocution. Place the microwave in a well-lit area to be able to locate the fuse.

2. Use a screwdriver to remove the outer cabinet of the microwave, and follow the power cord to the fuse. The fuse is located 2 to 3 inches within the microwave and is attached to the power board.

3. Observe the fuse to determine if it is blown. Blown glass fuses will produce burn marks on nearby surfaces, or the internal fuse wire will be black and melted, while ceramic fuses show no outward appearance of being blown.

4. Determine if a ceramic fuse is blown by testing it with an ohmmeter. If the ohmmeter reads zero ohms, your fuse is not blown. Other readings on the ohmmeter show that your fuse is blown.

5. Replace the blown fuse by popping it out of its holder, and snapping a new fuse in its place. Tighten the fuse clips by squeezing them together with your fingers.

6. Replace the outer cabinet of the microwave, and plug the microwave back into the electrical outlet. Test the microwave to see if it's working properly.

thanks.

I would check the door interlock switches and then if that doesn't fix it replace the invertor board and possibly magnetron.

There is an internal fuse on most microwaves, it will "Blow" if the door interlock switches are not happy, sometimes the fuse just blows, like some circuit breakers do.. get a few extra, replace it and see what happens..if it doesn't blow again, you're most likely ok, if not, there are more causes for the internal fuse to blow, beyond the interlocks, it's not going to be cheap.

This microwave has three door interlock switches and a fuse that are easily replaced by the consumer. Unplug the microwave. Remove the cover by unscrewing the 5 screws on the cover. Four are on the back, one on the lower right. One or more of the screws may be torx T15S (security)(bit available at hardware stores). As in all microwaves the capacitor should be discharged by shorting the cap terminals together. Note that the three switches are in a single black plastic carrier. Remove the two screws securing the carrier and the switches can be released by hand. Replace one at a time so as not to confuse the wiring which is push on spade terminals. Replace the fuse with a 20 amp 125v slow blow (radio shack). Do not plug in power until all the switches are reinstalled as a safety feature will cause the fuse to blow again. If fuse blows repeatedly it is most likely that all three interlock switches are not closing properly. Check to make sure that all switches are seated correctly in the black plastic switch carrier and that the 2 carrier screws are tight. Observe the switches as the door is closed. Replace switches and/or carrier as needed. While the cover is off you may want to clean off the fan and/or replace the bulb. Also check for proper seating of the control board connections.

try push in and turn

Possibly the interlock monitor switch is bad or out of adjustment. This switch is designed to create a short circuit across the power line (and then blow the fuse) if you attempt to defeat the door interlock and operate the oven with the door open. A shorted capacitor or diode could also cause the fuse to blow. Because of lethal voltages inside and the possibility of microwave leakage if repairs aren't done correctly, you are best off leaving microwave service to professionals.

The Interlock Monitor Switch is an added
safety check on the Primary and
Secondary Interlock Switches. If the
Primary and Secondary Interlock Switches
allow the oven to operate with the door
open, the Monitor Switch will blow the
fuse.

You can get more information about adjuting the interlock switch from this link

http://136.166.4.200/contents/Microwave/LMVM1935xx/LMVM1935xx_Service_Manual.pdf

sections 7-11 thru 7-12 discuss the door interlock adjustment that will cause the 20A fuse to blow if it isn't set up right. I hope this helps you...