MW8991SB Microwave Door Switch question

[kfw01]

Model Number

MW8991SB

Brand

Age

More than 10 years

Hi,

Have what I hope is an easy question. Am troubleshooting my Emerson microwave (light comes on, timer counts down, but no fan/noise, doesn't heat). As near as I can tell it's a door switch problem, seems fairly common.

Accessed my door switches (3 of them, part #5E4 10T105, KW3A) and tried continuity test w/ multimeter. All seem to be the exact same part, but with 2 of them, get no continuity signal unless I press down on the activator button (which is expected if i'm understanding how it works correctly...switch in normally closed mode, button gets pressed by door latch, allowing switch to open and power to flow).

But on the 3rd switch, I get the continuity tone on the meter before I press down on the switch, and no continuity when I do press on the switch. Is this my bad switch? Not sure why this behavior would be opposite of the other 2 where it appears to be the exact same switch. I know one of these switches gets installed upside down relative to the other two, but assuming the functioning of the switch should be the same no matter. Was expecting no continuity either way if the switch was bad.

Thanks in advance for the help.

 

[jeff1]

Hi,

Anti short switch works the opposite way the other 2 do...this is normal.
http://www.applianceaid.com/microwave-door-switch-help.php
http://www.applianceaid.com/component-testing.php
http://www.applianceaid.com/microwave-door-latch-replacement.php

(light comes on, timer counts down, but no fan/noise, doesn't heat). As near as I can tell it's a door switch problem

Door switch, door switch mechanism, door switch wire, door key are common trouble makers.

jeff.

 

[kfw01]

Thanks for the reply. So do I understand then those switches are all working correctly and this is another issue causing my problem? Or will replacing the switches potentially fix it?

Thanks.

 

[jeff1]

So do I understand then those switches are all working correctly and this is another issue causing my problem?

Yes or you haven't checked them fully ( continuity is just one way ).

jeff.

 

[kfw01]

Microwave door switch question

One last question before I give up and just buy a new one!

(fairly mechanically inclined, but have never worked on a microwave/micro-switches before...am taking all precautions, unplugging/discharging capacitor etc)

So I found a bad microswitch (opened it up, and see corrosion...can see how when pressing the switch it does not work properly). The only problem is, that I don't remember which switch it was (had taken all 3 out to test and didn't note which went where...initially thought they were all the same). I bought an identical replacement switch to the one that is corroded, but when I reinstall, the 20amp fuse where the power comes into to microwave keeps blowing. Would this be due to switches being installed incorrectly? Or should it still work, but in the opposite way it was intended?

Guessing my ultimate question would be which type of switch (normally open/normally closed) goes into which location (have primary up top, monitor in the middle, and secondary at the bottom).

And a question about switches in general...identifying normally open vs closed. Is where the terminal comes out of the switch the indicator of if it being normally open or closed (see picture, is the top switch in the picture a normally open one, and the bottom a normally closed one?).

Thanks again for the help.
Hoping if I just figure out which switch to put into which location this will correct the issue for me.

 

[jeff1]

Normally I see the upper one in your pic in the top and bottom spots and the lower one in your pic in the middle spot.

2 should open and 1 close when the door is opened.
2 should close and 1 open when the door is closed.

jeff.