wmh1164xvs-2 micro doesn't heat up

Microwave Repair
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micro doesn’t heat up. I think it the thermal fuse or the magnetron. what do you guys think?

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What it does and what it does not besides heating?

Does it make any unusual noise?

Here are the breakdown diagrams and http://www.appliancepartspros.com/partsearch/model.aspx?model_id=5511851

Gene.

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The microwave doesn’t make any noises and everything works perfect except for the inability to heat up food.

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The problem can be a bad magnetron thermostat, a bad magnetron or a bad control board. You have to have a simple multimeter to perform some tests. Let us know when you will be ready.

Gene.

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Gene,

I am having the same problem with my Microwave/Oven combo (MODEL# KEMC377KBS0) and would like to try and determine which component needs replacing. Once i have a multi-meter, will you be able to give me instructions on how to test the components?

I’m pretty confident I can replace which ever component is bad - once i figure out which one is faulty.

Thanks for any help you can give…

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Hi Bryan,

We definitely can guide you through the troubleshooting process. Let us know when you will be ready.

Gene.

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Thanks Gene,

Couple quick questions to get me started.

  1. I’m assuming I need the oven to be connect to power before I can test the components, correct? The reason I ask, is because the oven is currently in my garage waiting to be installed in another house.

  2. If you were to make an educated guess what the top 3 components that may be bad causing the microwave to run fine but not heat-what would those be? I’m thinking I may go ahead and buy them so i can have them on hand sooner and just return what i don’t use. My thinking is go ahead and purchase the Magnatron and the fuse. What else would you suggest i purchase.

  3. Do you recommend i get a Digital or Analog Multi meter.

thanks

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— Begin quote from bryantay;765115

…1) I’m assuming I need the oven to be connect to power before I can test the components, correct? The reason I ask, is because the oven is currently in my garage waiting to be installed in another house…

…2) If you were to make an educated guess what the top 3 components that may be bad causing the microwave to run fine but not heat-what would those be? I’m thinking I may go ahead and buy them so i can have them on hand sooner and just return what i don’t use. My thinking is go ahead and purchase the Magnatron and the fuse. What else would you suggest i purchase…

…3) Do you recommend i get a Digital or Analog Multi meter…

— End quote

  1. It’s very good to have it in a garage for troubleshooting and/or repair. You will need the oven powered up only at the final step to see if it’s fixed or not.

  2. So far it is unpredictable.

  3. I really don’t see any difference. You can find more information in of our previous threads: http://forum.appliancepartspros.com/oven-repair-including-ranges-cooktops/4810-how-check-continuity-ohmmeter.html

Gene.

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Thank Gene,

So i’m ready to start testing. I’ve accessed the microwave compartment where the Magnetron and other components are located.

I’ve discharged the capacitor (as best as i can tell the capacitor had no energy stored. it’s been sitting a few weeks)

I have my Digital Multi-meter and have check the fuse (27 in this diagram) it appears the fuse is fine.

What would be the next thing you would check?

How do you test the magnetron?

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Hi Bryan,

Attached to this post you will find some instructions as well as the tech sheet with the wring diagrams.

You also have to check both fuses, the door switches, the cavity thermostat (TOD) and the magnetron thermostat (TOD). All of them have to be checked for continuity.

Here are the breakdown diagrams and http://www.appliancepartspros.com/partsearch/model.aspx?model_id=265254

Gene.

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Thanks Gene,

I tested everything except for the switches.

Couple questions first:

  1. How do you test the switches? the 2 switches that are activated when the door closes have 3 leads coming off of them. I’m not sure what leads to touch with the MM and what i’m looking for. (continuity or no continuity??)

  2. I’m using a Digital MM rather than an Analog MM. The instructions state to set the MM to R x 1 or R x 1K. What is the equivalent value on a digital MM? My meter has values of 2M, 200k, 20k, 2k and 200.

  3. What should i do with the wiring diagram you attached to the post? i have no idea how to read that thing :slight_smile:

With that in mind, I went ahead and check everything but the switches the best I could and just tested each component using multiple values. Here is what I found.

  • Magnetron: Appears to be OK. I got the same reading as stated in the instructions.

  • Capacitor: Appears to be OK. When I touched the leads to the terminals, the MM would "jump" to several ohms then quickly go back to 1 (1 is infinity correct?) When i touched the leads tot he terminals and the chassis, the MM read 1

-Transformer: Seemed to be OK but i’d like to test it again after you tell me what the R X 1 equivalent is an my DMM. Also, when the instructions say touch one lead to the chassis, does that mean touch it to some metal of the microwave frame or touch it to the transformer itself?

-Diode: Best I can tell, this is BAD. The MM reads 1 no matter which way I touched the anode and cathode. I couldn’t get it to read continuity (0 on the MM) no matter what I tried. Could the Diode be responsible for the microwave not heating? if so, i’m curious how the Diode would cause this problem.

-Magnetron thermostate: Appears to be OK. Has continuity. I could not find the other thermostat you said to test. What part is it in the parts diagram?

Thanks again for your help. I know i’ll probably need to re-test everything once i have an answer to question #2 above.

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UPDATE:
So as of now, I can’t seem to determine whether or not the diode is good. after searching ways to test the diode I found that in a lot of cases, multi-meters don’t have enough power to test a diode and will show infinity in both directions. So i’m thinking that’s whats happening to me because I happen to have another microwave in my garage that i’m told works (however, i haven’t verified that) and the diode in it is giving the same reading - infinity both ways.

So, i happened across this video showing a way of testing the diode using AC power. When doing this test on a good diode the meter is supposed to show around 60 volts. Problem is when I do this test on either of the two diodes I get a reading of 118.5 on both.

So again I’m left unsure weather the diode is good or not. Seems odd to me that both diodes would be bad and showing the the same readings when tested.

HELP!

I still need to test the switches (whenever i figure out how to test them properly) …probably be able to find a video online. And I also need to test the other thermostat once i’m able to figure out were that sucker is.

I hope i’m not confusing you (Gene) with all this extra information. just trying to be thorough.

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Hi Bryan,

Sorry for the delay.

So far the diode looks very suspicious. I would recommend to test it using the instructions from one of our previous threads: http://forum.appliancepartspros.com/microwave-repair/19868-diode-testing.html

Set your meter on DC voltage.

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So I tested the Diode with an older car battery that I had.

The battery reads 10.19 when I hook the meter to it. When I add the diode, I get a reading of 6.58. When I reverse the diode, I get a reading of 0.

That’s a good diode right?

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Yes, it is good.

How to test switches? Any switch terminal is marked. It can be: COM - common, NO - normally open and NC - normally closed. When you check the switch for continuity, you have to do it twice: with the button not pushed in and with the button pushed in all the way. In the first case the correct reading is: COM-NO - open, COM-NC - closed. In the second case, accordingly, it should be close and open. The wires should be removed prior to testing.

Set the meter on 200 for all continuity tests.

The cavity thermostat is shown as #30 at the [B]diagram[/B].

Gene.

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Thanks for the reply Gene,

I checked the switches (found and checked 3 switches) All three show to be working fine.

I also located that second thermostat and it checked out fine as well.

So at this stage, I’m stumped. I’ve checked everything that I know to check and everything appears to be in working order.

I guess it may now be time to call in a professional, however, any other ideas you may have would be much appreciated.

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Hi Bryan,

The problem is that all of the above parts besides the magnetron can be tested instrumentally with very reliable test results. The magnetron still can be bad even if it did pass the continuity test. So, before you will call anybody I would recommend to order the magnetron and give it a try.

You can order the OEM magnetron or you can order the aftermarket one with the same parameters but for less money.

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Thanks Gene,

Will the aftermarket Magnatron fit the same as the original? There are no pictures of it to verify that is the same "shape" as the original. Would you recommend the aftermarket or the OEM?

Also,

I went back and checked the high voltage transformer with the MM set to 200 (as you suggested) everything checked out except for one possible exception:

The service manual states; (also see image attached):

My transformer doesn’t have a light yellow secondary wire but it does have a white secondary wire so i assume that it’s the correct wire because the other 2 secondary wires are red. Anyway, when i tested it as stated, i get a reading of 90.5 rather than 0.

Do you think this may be an area of concern? All other connections tested fine.

I think i’ll still go ahead and purchase the Magnatron and see if that fixes it.

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Last question to add to my last post.

Considering everything that i’ve tested to this point, if you add in the fact that the Microwave has a louder than normal Buzz when it’s running, what do you think (best guess) would be causing the buzzing sound.

thanks

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Hi Bryan,

The instructions for the high voltage transformer test has an error. Probably mistyping. The reading you got on the high voltage winding is good. I don’t think there is anything wrong with the transformer.

On the other side, the excessive noise points to a faulty magnetron.

As I mentioned earlier, the aftermarket magnetron has the same parameters as the OEM. Otherwise I would not recommend it.

Gene.