# Microwave won't heat, help please....



## TheBobmanNH (Oct 23, 2012)

"Everything else works fine on the microwave."

Isn't that the only thing microwaves do?


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## djlandkpl (Jan 29, 2013)

It could be one of the safety switches that's preventing the magnetron from working. I don't have a GE. Mine is a Wolf but I believe the guts are made by Sharp. My oven work look like its working but it would not heat the food. Turns out one of the safety switches was getting hot and it shorted out. There could be 3 or 4 of them in your oven. Look around the door area for them. Might look like this:


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## hardwareman (Oct 9, 2010)

microwave won't heat: it could be several things. The only way to narrow it down is to do live power tests inside the micro. Are you comfortable with that? If so I can walk you through it, but be warned that there is 4000 volts of electricity going to some parts! Do you have a digital volt meter?


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## ktkelly (Apr 7, 2007)

I'd start with the door switches.

Might take no more than a visual inspection.



Very common problem with GE microwaves.


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## Ralph III (Oct 7, 2011)

Thanks for the quick replies! 




hardwareman said:


> microwave won't heat: it could be several things. The only way to narrow it down is to do live power tests inside the micro. Are you comfortable with that? If so I can walk you through it, but be warned that there is 4000 volts of electricity going to some parts! Do you have a digital volt meter?


I have a couple of digital voltmeters but the one I use most often is this _GreenLee CM-600_. Just tell me what you'd like tested and don't worry safety first. I've done construction and electrical most my life and do understand the amount of power capacitors (also a photographer) can have. Note: Not as a contractor but as a homebuilder and as my Dad was a contractor/engineer. 

Do you need more pictures of the unit so I know exactly what you are talking about?

Ralph


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## hardwareman (Oct 9, 2010)

first things first, do you have the wiring diagram handy? No biggy if you don't we can still do this. Microwaves are divided into 2 sections, the low voltage side( 110volts) and the high voltage. Low voltage will include the control panel, door switches and the low side of the step up transformer. We can eliminate the low voltage side by taking a voltage reading at the low side of the transformer. Here is were the diagram would be nice to have since there will be 4 wires on the transformer and you don't want to get the wrong side. By the looks of yours ( I can only see half of it) the white wire on the bottom and I would assume a black wire that I can't see is going to be your low side. Check for 110 volts here, if you have it then everything on the low voltage side is working and the problem will be on the high side, either the diode, the capacitor or the mag tube.


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## Ralph III (Oct 7, 2011)

hardwareman said:


> first things first, do you have the wiring diagram handy? No biggy if you don't we can still do this. Microwaves are divided into 2 sections, the low voltage side( 110volts) and the high voltage. Low voltage will include the control panel, door switches and the low side of the step up transformer. We can eliminate the low voltage side by taking a voltage reading at the low side of the transformer. Here is were the diagram would be nice to have since there will be 4 wires on the transformer and you don't want to get the wrong side. By the looks of yours ( I can only see half of it) the white wire on the bottom and I would assume a black wire that I can't see is going to be your low side. Check for 110 volts here, if you have it then everything on the low voltage side is working and the problem will be on the high side, either the diode, the capacitor or the mag tube.


Thanks Hardwareman. Here are a couple of more pictures to insure I have everything noted correctly. There is a black and white wire coming off of what I assume is the microwave transformer. I marked the Diode with a "D" as it comes off of the capacitor and is then grounded. I will try and post a pic of the schematics in a little bit, if I can find it. Note: I can only read very very simple schematics. I leave that stuff to the experts....

Ralph


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## Ralph III (Oct 7, 2011)

Hardwareman. I tested voltage on both the white and black wires coming off of the transformer, denoted "B" and "W" in picture above (post #8). No power showed on either one. 

In testing, I plugged the unit in and checked for power on each leg with use of a chasis ground. I then used both probes on my voltmeter to check both legs simultaneously, as when testing for 240v, and still nothing showed. I tested my voltmeter on the outlet and it is working properly 120v. Note: I didn't actually start the unit but just had it plugged in.


FYI: I cannot find any schematics listed anywhere (bottom/top/sides/Interior). There is only a warning label in regards to some switches as shown below.

What else should I test?

Ralph


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## funfool (Oct 5, 2012)

Just saying, I had a really good friend that wanted to fix his broken microwave.
He was electrocuted and died instantly.
He had a wonderful funeral, over 200 showed up. He left behind a beautiful wife and 2 young boys.

How important is this microwave to you?


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## hardwareman (Oct 9, 2010)

black wire/white wire on transformer, hook up your meter to those two wires. Be safe and jab your leads into the wire protector so it holds your leads and you can get your hands out of there. Now turn microwave on and check for 110 volts. Safety is very important here, if you do not feel comfortable with this then please stop.


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## Ralph III (Oct 7, 2011)

funfool said:


> Just saying, I had a really good friend that wanted to fix his broken microwave.
> He was electrocuted and died instantly.
> He had a wonderful funeral, over 200 showed up. He left behind a beautiful wife and 2 young boys.
> 
> How important is this microwave to you?


I understand where you are coming from and if at any time I ever feel uncomfortable then beleive me you, I will not test.

Safety has always been my first priority as I was raised working around electricity all my life...


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## Ralph III (Oct 7, 2011)

hardwareman said:


> black wire/white wire on transformer, hook up your meter to those two wires. Be safe and jab your leads into the wire protector so it holds your leads and you can get your hands out of there. Now turn microwave on and check for 110 volts. Safety is very important here, if you do not feel comfortable with this then please stop.


*CORRECTION: I AM GETTING 120V AT THE TRANSFORMER!* 

I tested as you stated; hooked up voltmeter to black and white simultaneously, turned microwave on, and do get 120v reading.

*I PREVIOUSLY STATED I WASN'T GETTING ANY VOLTAGE BUT IT WAS DUE TO THE DOOR BEING AJAR AND CONSEQUENTLY NOT MAKING GOOD CONTACT WITH SWITCH.* 

Ralph


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## hardwareman (Oct 9, 2010)

no voltage means you either have a bad door switch, remove each one a do a continuity check, or a bad board. Check the switches, I'm sure you'll find one bad.


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## Ralph III (Oct 7, 2011)

hardwareman said:


> no voltage means you either have a bad door switch, remove each one a do a continuity check, or a bad board. Check the switches, I'm sure you'll find one bad.


*UPDATE:*

In looking at the switches I noticed one switch wasn't closing properly as I had the microwave resting partially on the door. 

Upon repositioning the microwave and retesting the transformer, I do indeed show 120v.

What next?

Thanks,
Ralph


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## tulipden0907 (Mar 13, 2013)

LÃªn nÃ*o lÃªn nÃ*o


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## hardwareman (Oct 9, 2010)

does it still not heat?


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## Ralph III (Oct 7, 2011)

hardwareman said:


> does it still not heat?


 
*Correct, the unit does not heat!*

I just erred in allowing the microwave door to rest on my bench in testing, which caused it not to fully engage one switch and hence no power initially showed on the transformer. This is a large over-the-range microwave so the door is never meant to rest on anything.

What should I test next?

Ralph


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## Protocol. (May 31, 2012)

Check the microfarads of the cap. Resistance of the coil on the mag should be 0.1 ohms or less. Diode could be shot. no real way to test I would recommend just getting a microwave diode and replacing, it really shouldn't be expensive, under 10 bucks.

If the primary coil of the transformer is getting 120V then I'd be looking at the HV side. Do you have an ammeter? would help because you can test amps on high side.


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## Ralph III (Oct 7, 2011)

*Ok, I am getting it to heat now whereas before it wouldn't? So I'm not sure what the issue is? Please see the post below.* 






Protocol. said:


> Check the microfarads of the cap. Resistance of the coil on the mag should be 0.1 ohms or less. Diode could be shot. no real way to test I would recommend just getting a microwave diode and replacing, it really shouldn't be expensive, under 10 bucks.
> 
> If the primary coil of the transformer is getting 120V then I'd be looking at the HV side. Do you have an ammeter? would help because you can test amps on high side.


Hello Protocol,
1) You're going to have to be specific in what you'd like me to test as I do not know what "microfarads" nor where/how to test the HV side? 

2) I did test the LV wires(120v) going to the transformer as Hardwareman had suggested. Those do show 120v. 

3) I just tested the amperage of the two wires coming off of the transformers winding. One side was varying quite a bit (3.5-12amp) during a one minute heating test. The other side stayed constant at around 4.0amps with a one minute heating test but did jump up to 10.0amps right before shutting off. You could really hear it draw when it went from the 4.0amps up to 10.0amps. 

I immediately retested it and this time it stayed constant at around 10.0 amps. It never dropped down to 3.5 or 4.0 amps as the prior test. With that I decided to try and heat some water and sure enough it heated the water??? 

Is it possible something is going bad and the unit must be ran once or twice before it will actually heat? Becuase it definetly wasn't heating prior to this? This unit is out of a house of mine that I completely refurbished 4 years ago (everything brand new; plumbing/electrical/appliances, etc). My renter brought it to me because he stated it had stopped heating, such as it did several years ago. I then tested the unit several times myself and it wouldn't heat.... 

Thanks,
Ralph


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## hardwareman (Oct 9, 2010)

if it is heating now then you have either a door switch that is hanging up or a bad control board. If it is heating then you just eliminated everything on the high voltage side as those are not likely to be intermittent


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## Ralph III (Oct 7, 2011)

hardwareman said:


> if it is heating now then you have either a door switch that is hanging up or a bad control board. If it is heating then you just eliminated everything on the high voltage side as those are not likely to be intermittent


I just tested again and is heating properly. I went ahead and left my meter clamped onto one of the transformer wires (as shown in last pic) and upon start up it clocks around 14amps then settles around 10amps. Which would seem a correct sequence... 

As noted, the first time I tested with the meter clamped on it stayed around 4.0amps as shown. Now it is staying at 10amps and heating properly.

It would seem a bad switch wouldn't be an issue with varying voltage as such? Wouldn't it just either be an open (thus nothing) or closed (thus allowing power)? I will keep testing to see if it continues to heat. 

Please continue to follow in case I need more help.

Thanks,
Ralph


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## Protocol. (May 31, 2012)

Clamp meters can 'change' depending on where the wire is located. I've had this happen with my meter on several occasions. 

I would agree. Sounds like a door switch. You also shouldn't ever run a microwave without a load (water) placed inside. The waves inside an empty microwave can bounce back up the waveguide and destroy the magnetron or shorten its life.


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## Ralph III (Oct 7, 2011)

Protocol. said:


> Clamp meters can 'change' depending on where the wire is located. I've had this happen with my meter on several occasions.
> 
> I would agree. Sounds like a door switch. You also shouldn't ever run a microwave without a load (water) placed inside. The waves inside an empty microwave can bounce back up the waveguide and destroy the magnetron or shorten its life.


Well, that is the conclusion I'm coming to also. I think in taking it apart and then opening and closing the door, a switch that was possibly stuck or not seated properly is now working correctly again.

BTW, I've got a bowl of water in the microwave which has been used for testing. Right now everything is working perfectly but I will keep it several more days, to be sure no issue shows, before re-installing it.

I appreciate all the help!

Ralph


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