• ** 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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microwave humming, now not heating

dcw1

Premium Member
Joined
Jul 1, 2013
Messages
12
Location
Johns Creek, GA
Model Number
FMV152KSA
Brand
Frigidaire
Age
1-5 years
I have a Frigidaire microwave oven, model # FMV152KSA. Today I used it and when I closed the door after removing the food (timer off/no time on the counter), it was making a humming noise. Not as loud as when running the oven but audible if you were near it. Almost as if an appliance is "trying" to turn on
but can't--like it is stuck. When I opened the door, the humming would stop and the interior light would come on fine.
I then put some food in the oven, started the oven for about 30 seconds and it heated the food fine. No unusual noises when heating that food. But again, when I turned it off and closed the door, the humming would start again.
I unplugged it for about an hour and when I plugged it back in, the humming was gone but now it won't heat food. Besides that it operates as normal. The interior light, the buttons, the fan, the exterior lights, the timer, the start/stop buttons, the keypad all function properly. It turns on, the platter spins, but no heating of food. Again, the humming is now gone when it is off and the door is closed. Also, when the oven was working, if you set the "power level" to say 5 out of 10, you could hear when the oven's "heating unit" (for lack of a better term) would come on. It "cycles" on and off 50% of the time. At power level 10, it was always "on". Now audibly, whether at power level 10 or 5, that "power on" sound is missing.
Searching the internet, I've seen general comments that the control board is bad, the magnetron is bad, the transformer is bad, the capacitor is bad, the door latch is bad, the diode is bad, etc., etc.
I don't have the experience to "test" these parts but feel comfortable replacing them. But if I am go with a "hit-or-miss" part purchase I want the best chance of being right. So, what is the most likely defective part I am looking at needing given the above symptoms. I took the control panel out and it "looks" fine--no burnt or scorched areas. But that's all I got. Any help is appreciated. Thx.
 

jeff1

Appliance Tech - Moderator
Staff member
Joined
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Messages
24,574
Location
Ontario, Canada

dcw1

Premium Member
Joined
Jul 1, 2013
Messages
12
Location
Johns Creek, GA
OK, thanks for the reply. I can swallow the $50 in door switches as that is not in "new microwave" territory yet.

If not the door switches, what would be the next logical part to be malfunctioning given the above-described symptoms?

Thx again.
 

dcw1

Premium Member
Joined
Jul 1, 2013
Messages
12
Location
Johns Creek, GA
When you say "smart board" do you mean the control panel? Basically the touch pad with buttons and on/off switches? That comes out pretty easily. I see that is $117 but is just the board.
Main Control Board

RepairClinic Item # 1514706




Or would it likely need the entire unit?
Control Panel

RepairClinic Item # 1514839



This is the whole unit (touchpad, main board, frame) for $184.

Now we are approaching new microwave territory. Thx again for the responses.<o:p></o
 
Last edited:

jeff1

Appliance Tech - Moderator
Staff member
Joined
Oct 10, 2004
Messages
24,574
Location
Ontario, Canada
Sort of, but DO NOT get ahead of yourself....many more door switch issues than smart board issues!!

jeff.
 

dcw1

Premium Member
Joined
Jul 1, 2013
Messages
12
Location
Johns Creek, GA
Ok. I had the door switches tested and they are fine according to the electrician I took them to. He is at a parts store and did it as a courtesy. So, if I am going to the next step of the main control board, what and how do I test that? Does it need to be in or out of the microwave oven to test?
 

jeff1

Appliance Tech - Moderator
Staff member
Joined
Oct 10, 2004
Messages
24,574
Location
Ontario, Canada
I had the door switches tested and they are fine according to the electrician I took them to
Good to hear about the switches, but we normally check them in place in case something in the mechanism is not tripping the switch(s) correctly.

So, if I am going to the next step of the main control board, what and how do I test that? Does it need to be in or out of the microwave oven to test?
In would be best, and WHEN THE PROBLEM IS OCCURING. The main one has wires attached and can be ohmed easily ( has continuity when it shouldn't have continuity ), others you may tap on when stuck/sticking and usually opens up and starts to work again.....a popcycle stick or such works well.

jeff.
 
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