CFMV145--thermal Cutout Question

Try using the VOM
First check is the main fuse of the unit. On countertop units, you will need to take the shell off. The fuse will be close to where the cord comes through into the unit. OTR units, this main fuse is usually behind the control panel or possibly behind the vent. Usually the fuse is obvious if blown, otherwise test with an OHM meter, if open, replace fuse.
Some brands will also have a thermal cut-off fuse in the incoming voltage line to the control board. Older Maytags and Samsungs have this fuse in it. This thermostat looking fuse is usually above the oven cavity somewhere under the outside shell. Sometimes you can get to it through the vent of OTR models. Test with an OHM meter, replace if open.

A wild guess: the scraping noise was a motor bearing seizing up (fan or turntable). A thermal cutout blew when something overheated. This would have taken several minutes to happen.

Alternate, and more likely explanation: the scraping noise was actually high-voltage arcing in a failed component, most probably the voltage doubler capacitor. This would blow the fuse. Replace both the capacitor and diode; the diode was probably overloaded and could fail at any time if it hasn't already. At $5-$10, it's cheap insurance against having to fix the thing twice.

If the 20A fuse is blowing, it is often the high voltage transformer or magnetron. If this is the case, and the microwave is not under warranty, replace it. Residential microwaves are generally considered disposable. Parts and labor are just too expensive. A magntron or transformer can cost more that half the cost of a new microwave.

Chances are the magnetron overheated and the blew the thermal cutout (TCO or thermal fuse), thus protecting the magnetron.

Bacon has a fairly low moisture level and when can cause overheating if there's no water load in the oven.

That said, a microwave can be dead for many reasons.

It may be the fuse, which is usually located on the floor of the oven behind the control panel or between the door switches.

If the fuse is good, it may be an open thermostat or thermal cutout (TCO) / thermal fuse on or near the magnetron or on top of the cavity / body of the oven.

If it goes dead for a while during or after cooking then comes back on, the magnetron is probably overheating and causing the magnetron thermostat to open.

Then when it cools, it closes the circuit and allows power through again.

When checking thermostats, if it has a hood fan thermostat, that should read open, as opposed to the others, which should read closed.

If it went dead almost immediately after pressing the Start pad, that's usually a shorted high-voltage capacitor.

If it went dead a few seconds after pressing the Start pad, that's usually a failing high-voltage transformer.

If it goes dead or blows the breaker (or GFI) when you plug it in or open or close the door, then there's a problem with a door switch or door switch mount.

If it's intermittent or random, it may be a bad connection, usually on the control board or a loose fuse holder, or even an intermittent fuse.

You should do a continuity test on the fuse while it's in the holder (with the microwave unplugged, of course) then turn the fuse by hand or take it out and put it back in, then test it again.

If you remove the fuse, then press the meter leads against the ends, it can allow internal contact to be made and make a bad fuse appear to be good.

If you or someone you know decide to look into it, we have critical safety information and disassembly information at our site, and our link is at our listing here on FixYa.

There should also be a "mini-manual" hidden inside the unit behind the control panel or hidden on the left side behind the grille, which is very helpful when troubleshooting & testing.

You can usually find helpful exploded view diagrams and order parts by entering your full model number here.

We're happy to help you and we'd appreciate your thoughtful rating of our answer.

Does the inside light come on when the door is opened?

If not, then I'd say the internal fuse or thermal cutout / thermostat has failed.

A microwave can be dead for many reasons.

If the fuse is good, it may be an open thermostat or thermal cutout (TCO) / thermal fuse on or near the magnetron or on top of the cavity / body of the oven.

If it goes dead for a while during or after cooking then comes back on, the magnetron is probably overheating and causing the magnetron thermostat to open.

Then when it cools, it closes the circuit and allows power through again.

When checking thermostats, if it has a hood fan thermostat, that should read open, as opposed to the others, which should read closed.

If it went dead almost immediately after pressing the Start pad, that's usually a shorted high-voltage capacitor.

If it went dead a few seconds after pressing the Start pad, that's usually a failing high-voltage transformer.

If it goes dead or blows the breaker when you plug it in or open or close the door, then there's a problem with a door switch or door switch mount.

If it's intermittent or random, it may be a bad connection, usually on the control board or a loose fuse holder, or even an intermittent fuse.

You should do a continuity test on the fuse while it's in the holder (with the microwave unplugged, of course) then turn the fuse by hand or take it out and put it back in, then test it again.

If you remove the fuse, then press the meter leads against the ends, it can allow internal contact to be made and make a bad fuse appear to be good.

If you or someone you know decide to look into it, we have critical safety information and disassembly information at our site, and our link is at our listing here on FixYa: http://tinyurl.com/yzjozk

We're happy to help and we appreciate your thoughtful rating of our answer.

Yes, there will be a fuse and also on or above the magnetron, there will be a thermal cutout or thermostat, and one on the top of the cavity.

But here is our long answer on a dead microwave:

A microwave can be dead for many reasons.

If the fuse is good, it may be an open thermostat or thermal cutout / thermal fuse on or near the magnetron or on top of the cavity / body of the oven.

If it goes dead for a while during or after cooking then comes back on, the magnetron is probably overheating and causing the magnetron thermostat to open. Then when it cools, it closes the circuit and allows power through again.

When checking thermostats, if it has a hood fan thermostat, that should read open, as opposed to the others, which should read closed.

If it went dead almost immediately after pressing the Start pad, that's usually a shorted high-voltage capacitor.

If it went dead a few seconds after pressing the Start pad, that's usually a failing high-voltage transformer.

If it goes dead or blows the breaker when you plug it in or open or close the door, then there's a problem with a door switch or door switch mount.

If it's intermittent or random, it may be a bad connection, usually on the control board or a loose fuse holder, or even an intermittent fuse.

You should do a continuity test on the fuse while it's in the holder (with the microwave unplugged, of course) then turn the fuse by hand or take it out and put it back in, then test it again.

If you remove the fuse, then press the meter leads against the ends, it can allow internal contact to be made and make a bad fuse appear to be good.

If you or someone you know decide to look into it, we have critical safety information and disassembly information at our site, and our link is at our listing here on FixYa: http://tinyurl.com/yzjozk

Please feel free to contact me directly if you need more help.

We're happy to help and we appreciate your thoughtful rating of our answer.

William E. Miller, AS-EET
[email protected]
http://www.microwavedisplay.com

I woulds first suspect a blown internal fuse or a thermal cutout on the magnetron in your case, but a microwave can be dead for many reasons.

If it goes dead for just a while during or after cooking then comes back on, the magnetron is probably overheating and causing the thermostat to open. When it cools, it closes the circuit and allows power on again.

If it's intermittent or random, it may be a bad connection, usually on the control board or fuse holder.

If it went dead almost immediately after pressing the Start pad, that's usually a shorted high-voltage capacitor.

If it went dead a few seconds after pressing the Start pad, that's usually a failing high-voltage transformer.

If the fuse is good, it may be an open thermostat or thermal cutout on or near the magnetron or on top of the cavity / body of the oven.

If you or a friend decide to look into it, we have critical safety information and disassembly information at our site, linked here on Fixya: http://tinyurl.com/yzjozk

Please write back with more details if you need further help.

We appreciate your thoughtful rating of our answer.

Dead? You mean no power, no lights, no beeps, nothing?

It's most likely a blown thermostat / thermal cutout on the magentron, based on your info.

But if you can post the model number I may be able to steer you better.

More generic info:

A microwave can be dead for many reasons.

If it goes dead for a while during or after cooking then comes back on, the magnetron is probably overheating and causing the thermostat to open. When it cools, it closes the circuit and allows power through again.

If it's intermittent or random, it may be a bad connection, usually on the control board or fuse holder.

If it went dead almost immediately after pressing the Start pad, that's usually a shorted high-voltage capacitor.

If it went dead a few seconds after pressing the Start pad, that's usually a failing high-voltage transformer.

If the fuse is good, it may be an open thermostat or thermal cutout on or near the magnetron or on top of the cavity / body of the oven.

If you or a friend decide to look into it, we have critical safety information and disassembly information at our site, linked here on Fixya: http://tinyurl.com/yzjozk

check the diode and the cap they like to go bad.good luck

Check if there's a fuse on the front panel.i'f had it on other makes.replace fuse and it should be ok.