• ** REMEMBER! **The microwave can still shock you even unplugged!!

    ALWAYS discharge the high-voltage capacitor first if you even think your hands will come close to any HIGH VOLTAGE components.

    Jeff mentions this: Anything in the high voltage ( magnetron, capacitor, diode, wires to and from ):
    ...Use a metal ( not the shiny chrome type ) screw driver with a insulated handle to short across ( touch both at the same time ) the terminals of the high voltage capacitor to discharge it.

    From Jeff's site: http://www.applianceaid.com/component-testing.php

    Jake
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FIXED Door Switch AND fuse question

nd_rawlins

Premium Member
Joined
Oct 16, 2013
Messages
9
Location
Fruitland, Idaho
Model Number
MMV4205BAB
Brand
Maytag
Age
6-10 years
My Maytag microwave (mod# MMV4205BAB) does not heat food, but retains all other functionality (light, fan, turn table, display, etc). I performed some basic tests on a lot of components with my multimeter (capacitor, diode, thermostats, transformer, and magnetron) everything looked ok. Then I found that the HV fuse was blown (my unit has 2 fuses). I am worried that a new fuse will blow if I just swap it out...especially if there is something else wrong that caused the fuse to blow.

I tested the door interlock switches and found something strange. The bottom interlock (I think it is the primary) tests normal when the wire leads are disconnected. But when I test the continuity of the wires by themselves (disconnected from the switch) there is about 75 ohms of resistance. Should this be happening? Or does it mean that I have a short somewhere in the wiring?

Thanks in advance for any help!!
 

jeff1

Appliance Tech - Moderator
Staff member
Joined
Oct 10, 2004
Messages
24,835
Location
Ontario, Canada
Hi,

I tested the door interlock switches and found something strange. The bottom interlock (I think it is the primary) tests normal when the wire leads are disconnected. But when I test the continuity of the wires by themselves (disconnected from the switch) there is about 75 ohms of resistance.

With the wires on, you are accidentally checking something attached to those wires....have to isolate ( wires off ) to ohm test.

Then I found that the HV fuse was blown (my unit has 2 fuses).

HV fuse? You mean a thermostat? I only saw one fuse, on the filter assembly.

jeff.
 

nd_rawlins

Premium Member
Joined
Oct 16, 2013
Messages
9
Location
Fruitland, Idaho
Thanks for the reply. I thought that same thing about the resistance when I looked at the wiring schematic.

There are 2 fuses, both are 250V 20 amp ceramic fuses. One of them cuts power to the whole unit. The other is called the HV transformer fuse (the one that was blown) on the schematic and only cut power to the high voltage components.

Going to go ahead and just try replacing the fuse and see if it blows again...fingers crossed!
 
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