FIXED AMV5206BAC Amana Microwave won’t start

[Dmiller]

Model Number

AMV5206BAC

Brand

Amana

Age

6-10 years

Microwave stayed running after door was opened Turned off when closed. Then failed to run after I used a multi meter to check thermostat. In front behind control panel. I got continuity on one. Not in other
I also checked the door switches. The primary lower had continuity before pressing button. Which I believe indicates a bad switch. The secondary. Top. Had continuity only after the button was pushed. My question is; Could the faulty door switch be the problem it don’t turn off. And could it have blown the fuse as a result of being faulty. All the timers and display function properly when turned on. The magnetron does not engage to heat

 

[Wx4usa]

I hope this helps.
Make sure you unplug the microwave and stay away from the HV High Voltage section.

Let's discuss the thermal fuses first.
There are four on your model.
1. One is on the magnetron. It will fail if the magnetron gets too hot. Usually because it is failing or the fan is dead. (Both are fairly rare) Or a child inadvertently hit 60 minutes on a potato instead of 6.
2. One is the cavity thermal fuse. Same as above. A child may have inadvertently hit 60 minutes on a potato instead of 6. It is a bit hard to reach physically, but can be tested without disassembly.
3. One is called the hood tco. It actually operates the opposite. It will be open normally and close if the cooktop on the stove below gets too warm. This thermal fuse will turn on the vent fan to cool the microwave. It will reset when temps lower. It appears you tested this one and its ok.
4. One is the bottom thermal fuse that will fail if the cooktop down below gets too hot. Opposite of number 3 above. The hood and bottom tco are behind the controls board and user interface. It also appears you tested this one and it s OK.
1, 2 & 4 above should have continuity. 3 no continuity unless it is hot.
Your measurements of the two thermal fuses behind the control board on the bottom likely mean they are OK.

There are three switches on your model.

NOTE: On switches the term is 'Normally' ... Normally Closed NC or Normally Open NO. "Normal state' means door open. Do test them after you pull the plug off the switches. The circuit can affect the continuity test.

Switch one your primary switch is the bottom one. It is NO or normally open. Meaning door open, no continuity. Door closed, continuity.
Switch two is the monitor switch or the middle one. It is NC or normally closed. Meaning door open, continuity. Door closed, no continuity.
Switch three is the secondary switch or top one. It is NO or normally open. Meaning door open, no continuity. Door closed, continuity.

Your primary switch appears to be the culprit and yes, it blew the fuse via the monitor switch. You said "The primary lower had continuity before pressing button." It should have NO continuity when NOT depressed. It is in line with the HV High Voltage circuit and you will have no heat if it fails to close when the door is shut. You also said it blew the fuse. The monitor switch is the fail safe and will blow the fuse when the other switch is bad.

You'll need to replace the Primary Normally Open, Monitor Normally Closed, and fuse. (It is always recommended that you replace the monitor any time it shorts to blow the fuse.)

 

[Dmiller]

When I set my multimeter to tone. I got tone on the hood thermostat
When put on bottom thermostat I got no tone
I did check the push in fuses. On top back have tone
I did not check the cavity or magnetron thermostat
When checking secondary interlock switch. I dot tone after pushing button
When testing primary interlocking switch. I had tone before and after pressing button. The button failed to spring back mad rattle sound when shook

When testing the monitor switch. I have tone before button is pressed. And no tone after button is pressed.
I ordered a primary interlocking switch along with the bottom thermostat. Am I in the right path. Thank you. Your knowledge is greatly appreciated

 

[Wx4usa]

According to the schematic, the bottom tco will kill power to the microwave just like the current fuse...it is directly in L1.

The hood thermostat should have no continuity at room temp. It runs the vent fan if the oven gets too hot.

You are on the right path. From what you say, your primary bad, monitor and secondary test good.

Did the 250v 20a current fuse blow too? You actually have 2 fuses. One in the HV section (rare failure) and one on the filter board (common failure).

You can tell which one is the bottom tco by continuity from L1 the small lug on the ac wall power cord to the tco. The first stop after the wall plug and before the filter board is the bottom tco. Usually the bigger size black wires go to the bottom tco since it handles all the incoming L1 current. Can't tell from your picture. but they may be backwards. You can pull the tco out and look at the temp rating on them too. The bottom tco will have 0/32 for second temp. The hood tco will have two temps listed and they will be lower temps. The bottom tco is designed to kill the microwave if there is a fire on the cooktop. It assumes that the fans may run and you don't want excess oxygen feeding a stove fire, hence it kills the whole microwave.

If you have no power at all, the bottom tco may have failed and/or the round current fuse on the filter board may have failed. Did the filter board fuse test good? Its the small board shown in the attached image.

 

[Wx4usa]

By the way Mr. Miller, if the round 20a current fuse is good, you can test all of these parts with one continuity measurement. Bottom TCO, 20a fuse, mag TCO, and cavity TCO. One test lead to L which is the small lug on the ac power cord and one test lead on the black wire on the primary switch. Unplugged microwave of course. If you get a tone, these parts in blue are all good. If at first you don't hear a tone, insert your test lead in the other connector on the primary switch. This is a great way to check the mag TCO and cavity TCO since they are hard to reach. (The hood TCO isn't in a series line with main power so it won't matter for heating)

 

[Dmiller]

According to the schematic, the bottom tco will kill power to the microwave just like the current fuse...it is directly in L1.

The hood thermostat should have no continuity at room temp. It runs the vent fan if the oven gets too hot.

You are on the right path. From what you say, your primary bad, monitor and secondary test good.

Did the 250v 20a current fuse blow too? You actually have 2 fuses. One in the HV section (rare failure) and one on the filter board (common failure).

You can tell which one is the bottom tco by continuity from L1 the small lug on the ac wall power cord to the tco. The first stop after the wall plug and before the filter board is the bottom tco. Usually the bigger size black wires go to the bottom tco since it handles all the incoming L1 current. Can't tell from your picture. but they may be backwards. You can pull the tco out and look at the temp rating on them too. The bottom tco will have 0/32 for second temp. The hood tco will have two temps listed and they will be lower temps. The bottom tco is designed to kill the microwave if there is a fire on the cooktop. It assumes that the fans may run and you don't want excess oxygen feeding a stove fire, hence it kills the whole microwave.

If you have no power at all, the bottom tco may have failed and/or the round current fuse on the filter board may have failed. Did the filter board fuse test good? Its the small board shown in the attached image.
View attachment 70189There are 2 fuses like the white one above. They both have continuity this is the bottom try. Parts on the way. Ill let you know. Thanks

 

[Dmiller]

By the way Mr. Miller, if the round 20a current fuse is good, you can test all of these parts with one continuity measurement. Bottom TCO, 20a fuse, mag TCO, and cavity TCO. One test lead to L which is the small lug on the ac power cord and one test lead on the black wire on the primary switch. Unplugged microwave of course. If you get a tone, these parts in blue are all good. If at first you don't hear a tone, insert your test lead in the other connector on the primary switch. This is a great way to check the mag TCO and cavity TCO since they are hard to reach. (The hood TCO isn't in a series line with main power so it won't matter for heating)

View attachment 70190

Thank you great to know

 

[Wx4usa]

Here are the TCOs in your model. The one you pictured is the hood one and should be open at room temp. It has 70 on it.

 

[Dmiller]

So your saying the picture is the hood you. Not the bottom. It did not have any black wires attached to it. The one in the picture did not have a tone when checked. The other did. You said the hood tcu Has no tone at room temp. I thought the one in pulled in picture was bottom t I. Since it was located forward like in diagram but you said the bottom tvu shoud have the black wire running to it like the tcu in picture that is still installed. I think I prefer the wrong tcu. And if what you were saying about hood tcu no having continuity at room tp ( no tone on meter). And the the other tcu with black wire has continuity at room temp( tone on multimeter. The tcu may be fine. Since no tone on hood and tone on bottom. Are you positive the tcu in picture is hood?Am I correct on this assumption. I do know the primary door switch is definatly bad. Could this be the only problem that would cause the microwave to not run.? Are the 20 amp fuses on filter board universal. Can I purchase the fuses at possibly an automotive store. Since I can’t get the fusses without pitching the whole part. ?

 

[Wx4usa]

I believe the TCOs may have been backwards. Just put it back together the way it was and install your switch when it arrives and I think you’ll be fine. They are known for changing wire colors lol. Did you have lights or display on the control panel? I would stick with microwave fuses 250v 20a is different than pulling 20a at 12v

 

[Dmiller]

Yes all lights and controls function properly it just not run. I thought the same about there placement of tcu. The one I removed had the blue and purple wire. This tcu had no tone. As it should at room temp. I will reinstall the tcu I removed with a new primary door switch. And your saying this may be enough. Thank you for clarifying the wiring on the bottom tcu ( one with black wire. That is still installed in picture)
Hopefully the new switch solves the problem. Can I purchase a 20 amp from anywhere. I’m summing that the white fuses in the diagram you sent are universal or does it need to be the whole part purchase. Thanks agin

 

[Wx4usa]

Ok so if lights and control display works, your fuses and TCOs are all ok. I think the switch is all you’ll need. Yes any microwave fuse is good. But yours is ok or you’d have no power at all to the microwave or control board.

 

[Dmiller]

Ok so if lights and control display works, your fuses and TCOs are all ok. I think the switch is all you’ll need. Yes any microwave fuse is good. But yours is ok or you’d have no power at all to the microwave or control board.

New switch installed. Problem solved. O thing but the greatest of appreciation for everything. 10 stars

 

[Wx4usa]

Very glad to hear! Thank you for the update.