• ** 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

FGMV174KFB Microwave won't heat

Jacobariel

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Model Number
FGMV174KFB
Brand
Frigidaire
Age
6-10 years
The microwave powers on and the light comes on inside and tray spins but will not heat. I opened the unit and I know to not touch anything at all and to first decgarge the capacitor. I found a fuse that is not transparent in color but has a read streak. Is that normal or is it blown? See pic. Model FGMV174KFB
 

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Dan O.

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Fuse likely OK

I found a fuse that is not transparent in color but has a read streak. Is that normal or is it blown?
1.When those ceramic fuses blow there are no visible signs. It was marked for some other reason, maybe its amperage so it didn't get confused with others in the manufacturing process?
2. If the internal fuse had blown, usually nothing would operate afterward. No control functions either. Totally dead.
3. The fuse can be tested for continuity to see if it was electrically open or not. Infinite resistance = blown.

Just not heating could be due to a malfunctioning door switch, the control not powering the HV transformer, a defective HV transformer or maybe a defective magnetron tube. It would be somewhat unusual for the latter to occur 'out of the blue'. Magnetron tubes often fail over time.

It is going to require some investigation to pinpoint the cause. About the only simple thing to try is closing the door aggressively to make sure all the door switches are engaging properly.

JMO

Dan O.
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Jacobariel

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Thanks. You are correct. I removed the fuse and nothing powered on. I then placed it back and the power returned so it's not the fuse. I then put in a new diode and did not heat so it's not the diode. When I decharged the capacitor with a screwdriver there was no pop or discharge at all. Is that normal or could that be that the capacitor is bad?
The magnetron looked a little stained with light brown around the grill area that's around it. Is this normal from the years of use?
If I remove the magnetron how dangerous is it? I read to never touch the antenna.
 

Dan O.

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Discoloration

When I decharged the capacitor with a screwdriver there was no pop or discharge at all. Is that normal or could that be that the capacitor is bad?
Any charge could have been discharged already. It is possible to test the capacitor (see the following link). I don't know that it would exhibit your symptoms if it was bad.

LINK > Appliance Aid: Capacitor Testing

The magnetron looked a little stained with light brown around the grill area that's around it. Is this normal from the years of use?
Room air is blown through the magnetron tube to cool it. Cooking or smoke residue in the room air could stain it. I wouldn't be too concerned if the discoloration is just on the heat sink fins.

If I remove the magnetron how dangerous is it? I read to never touch the antenna.
I don't know what would be gained by removing it. There is a mesh seal around the antenna that shouldn't be disturbed or it could lead to microwave leakage.

JMO

Dan O.
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Jacobariel

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I wanted to remove the magnetron to test it. Also the microwave lid does not seal around the unit like before I opened it. In other words not a tight seal. Is that ok?
 

Dan O.

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I wanted to remove the magnetron to test it.
Any testing that can be done on the magnetron tube can be (and should be) done in place. The less disassembly the better.

Also the microwave lid does not seal around the unit like before I opened it. In other words not a tight seal. Is that ok?
Do you mean the cabinet? It won't hurt anything but should be put on correctly. I wouldn't leave it that way.

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Jacobariel

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Any testing that can be done on the magnetron tube can be (and should be) done in place. The less disassembly the better.


Do you mean the cabinet? It won't hurt anything but should be put on correctly. I wouldn't leave it that way.

Dan O.
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What setting do I place the volt meter to in order to test the magnetron and what do I look for?
 

Dan O.

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Continuity test

What setting do I place the volt meter to in order to test the magnetron and what do I look for?
The magnetron tube is tested for continuity or resistance.

LINK > How do I test for continuity?

A continuity check across the magnetron filament terminals should show continuity. A resistance check should indicate less than 1 ohm.

If there is a thermal protector attached to the magnetron tube, it should be tested for continuity as well.

To test for a shorted magnetron, set the meter on its highest resistance setting (eg. 1K, 100K, etc.). Test between the magnetron filament terminals and its metal housing. This test should indicate an infinite resistance. If there is any resistance, the magnetron is grounded and likely needs to be replaced.

Dan O.
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Jacobariel

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The magnetron tube is tested for continuity or resistance.

LINK > How do I test for continuity?

A continuity check across the magnetron filament terminals should show continuity. A resistance check should indicate less than 1 ohm.

If there is a thermal protector attached to the magnetron tube, it should be tested for continuity as well.

To test for a shorted magnetron, set the meter on its highest resistance setting (eg. 1K, 100K, etc.). Test between the magnetron filament terminals and its metal housing. This test should indicate an infinite resistance. If there is any resistance, the magnetron is grounded and likely needs to be replaced.

Dan O.
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Ok thanks. Basically I need to see less then 1 ohm to know that it is bad?
 

Dan O.

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What is easier for first time users. An analog or digital meter?
I only have an analog meter, and a cheap one. I don't need anything sophisticated to do continuity, resistance and voltage checks. I don't need resistance measurements down to the 0.00001 ohm.

But either would be fine if you read their instructions on how to operate them properly.

JMO

Dan O.
 

Jacobariel

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When you say check for a thermal protector are you referring to the magnetron thermal fuse?
 

Jacobariel

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I just checked using the meter set to diode mode. (This one beeps when there is continuity)The meter beeped with the capacitor and the magnetron and the other big transformer thing(Can't remember the name) and with the door switches. It did not beep with the diode nor with the thermal fuse. I guess I can say I have two parts that are bad the diode and thermal fuse. I'm just checking in with you to make sure I haven't missed something. See pic on meter setting. Thank you.

By the way is this the thermalfuse or thermostat on the pic?
 

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Dan O.

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It did not beep with the diode nor with the thermal fuse. I guess I can say I have two parts that are bad the diode and thermal fuse.
A more powerful meter is needed to properly test a microwave diode. The meter needs to have a 9 volt battery, most don't. So that part may not necessarily be defective.

By the way is this the thermal fuse or thermostat on the pic?
That is called the thermal cutout. Some might call it a fuse. There are 2 in your model. One is mounted on the base of the microwave, the other above the oven cavity.

While if either had no continuity it would definitely be defective, I don't see either's failure producing your symptoms. As near as I can tell from the wiring diagram, if the one on top of the oven cavity was defective it looks like it should stop the interior light, turntable motor, stirrer motor, cooling fan motor and the electronic control as well as heating, not just the heating. The one at the base of the unit should only stop the vent fan motor from running.

LINK > Thermal cutout, oven cavity

LINK > Thermal cutout, hood

I don't know what to tell you. Sorry.

Dan O.
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Jacobariel

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A more powerful meter is needed to properly test a microwave diode. The meter needs to have a 9 volt battery, most don't. So that part may not necessarily be defective.


That is called the thermal cutout. Some might call it a fuse. There are 2 in your model. One is mounted on the base of the microwave, the other above the oven cavity.

While if either had no continuity it would definitely be defective, I don't see either's failure producing your symptoms. As near as I can tell from the wiring diagram, if the one on top of the oven cavity was defective it looks like it should stop the interior light, turntable motor, stirrer motor, cooling fan motor and the electronic control as well as heating, not just the heating. The one at the base of the unit should only stop the vent fan motor from running.

LINK > Thermal cutout, oven cavity

LINK > Thermal cutout, hood

I don't know what to tell you. Sorry.

Dan O.
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Is the top thermal cutout on top of the magnetron? Also can you send again the thermal hood link? The one you sent has no part number. You've been really helpful. I really appreciate it.
 
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Dan O.

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Jacobariel

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As near as i can tell from the parts list, it looks to be on top of the oven cavity (not on the magnetron tube) just left of center.


Sorry. (They booth look the same however.)

LINK > Thermal cutout, hood

Dan O.
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The one on the picture that I had sent it says thermal cutout which is this
https://www.repairclinic.com/PartDetail/Thermoprotector/5304502765/4279474?modelNumber=FGMV174KFB
The other one that's on the top middle is
https://www.repairclinic.com/PartDetail/Thermal-Fuse/5303319550/634750?modelNumber=FGMV174KFB
One says thermoprotector and the other thermal fuse. They are different right? The one in my pic also has one on top plus a different one too?
 
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