• ** 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

Kenmore Over the stove Microwave

tebb23

Premium Member
Joined
Feb 15, 2011
Messages
7
Location
US
Model Number
721.8935090
Brand
Sears Kenmore
Age
More than 10 years
Hello all,

Last night my 20 year old microwave just stopped. I did some research today and found it had an inline fuse which I replaced and temporarily fixed the problem. However, once I turned the microwave on, just was testing it on a cup of water, it almost immediately blew the fuse again. This is happened both times while the microwave was running. Honestly if it didn't seem like such a bear to replace I would just go buy a new microwave, but it doesn't seem to be a slide it out, slide in a new one situation. Anyway, I am hoping someone can suggest a fix/solution to this issue, I am no expert, but have had pretty good success fixing many of the appliances around the house with the proper guidance. I have googled and youtubed this issue and searching the way I have, have come up empty.

Thank you in advance if anyone has an idea on what the heck could be blowing the fuses. :confused:
 

jeff1

Appliance Tech - Moderator
Staff member
Joined
Oct 10, 2004
Messages
24,008
Location
Ontario, Canada
Hi,

Depends on when the fuse blows...

Q - My microwave went dead when I opened the door ( same problem as closed the door ).
A - This often is a stuck or faulty door switch and it has blown the interior microwave fuse.

Q - My microwave blows the fuse inside itself as soon as I push the start button.
A - Usually a shorted high voltage capacitor...see components section.

jeff.
 

tebb23

Premium Member
Joined
Feb 15, 2011
Messages
7
Location
US
Good morning Jeff and thank you.

Both times, last night and this morning, it happened while the microwave was running.
 

tebb23

Premium Member
Joined
Feb 15, 2011
Messages
7
Location
US
Hi,

Depends on when the fuse blows...

Q - My microwave went dead when I opened the door ( same problem as closed the door ).
A - This often is a stuck or faulty door switch and it has blown the interior microwave fuse.

Q - My microwave blows the fuse inside itself as soon as I push the start button.
A - Usually a shorted high voltage capacitor...see components section.

jeff.
If the microwave has been off for several hours, does the capacitor lose it's charge? I am thinking I can replace it, I just want to be sure I don't get zapped, it has been off quite a while. The capacitor sits right up front and I can handle it fairly easily and just make notes on how everything reconnects.
 

jeff1

Appliance Tech - Moderator
Staff member
Joined
Oct 10, 2004
Messages
24,008
Location
Ontario, Canada
If the microwave has been off for several hours, does the capacitor lose it's charge?
No...it can, but no.

it happened while the microwave was running
As soon as you hit the start?...that is often a shorted capacitor.

Discharging a cap..

nuker101.JPG

Ohm meter testing a capacitor...
Capacitor Testing | Appliance Aid

I just want to be sure I don't get zapped
Once discharged, they are easy to replace and handle.

jeff.
 

tebb23

Premium Member
Joined
Feb 15, 2011
Messages
7
Location
US
No, not as soon as I hit the start button. The first time was about 7-10 minutes into heating something. The second time, after I had replaced the fuse, I only set it for 10 seconds and it popped the fuse 5 seconds in. So neither was a bang bang thing, both times the microwave came on, ran a bit then blew the fuse. I pulled the cap and am going to try that first, other similar issues I have read were fixed by replacing the cap.
Should I go ahead and replace that diode also? Or would that be a completely different set of malfunctions?

Thank you again Jeff for your time and patience in answering my questions.
 

jeff1

Appliance Tech - Moderator
Staff member
Joined
Oct 10, 2004
Messages
24,008
Location
Ontario, Canada
Should I go ahead and replace that diode also? Or would that be a completely different set of malfunctions?
Only if it tests as bad. Most times a bad diode doesn't blow the fuse, makes a load buzzzz noise and no cooking.

jeff.
 
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