Kitchenaid Microhood Microwave - No Power

[jacuze]

I was using my microwave to heat up some great chili and it began making a loud crackling noise and then it shutoff and the display went dark.  Here is what I've done so far:
1. Checked the breaker - It wasn't tripped
2. Checked the outlet and it had 120VAC.
I removed it from the wall, opened it up
3. Checked the fuse - Zero ohms (Good Fuse)
4. Plugged the microwave in and check both sides of the fuse holder, one lead on the case and then I touched one lead on each side of the fuse holder.  120VAC on both sides (Good).
5. Checked the magnetron - Across the leads I had 9.5 ohms. Each lead to the case of the magnetron -infinity
6. Checked the power through the door switches and I had 120VAC.
7. Checked the sensor on top of the magnetron: with power off - Infinity across the leads.  With power on 120VAC across leads which confirms it is open. Should this sensor be open?

I tried to download a service manual for any kitchenaid or whirlpool microwave, but I got a "timeout" webpage.

Any help on what I should look at next?

Thanks,

Jacuze

Model KHMS2050SSS2

[jacuze]

Update to my troubleshooting.

After looking at a few other manufacturers diagrams, I see that primary power goes through the sensor on top of the magnetron.  So I assume that it should be closed normally and open in a fault or possibly overheating condition.
I removed the leads from the sensor and shorted them together and plugged the microwave in.  Power to the display came on.  So I know the sensor is bad, but I'm still not sure about the magnetron.  Would the sensor going bad make the microwave hum louder than normal as it went bad?
I'll order a sensor, but need to know if 10 ohms across the leads on the magnetron is ok?  I've always thought it should be zero ohms.

Thanks,

Jacuze

[Repair-man]

Depends on which sensor you mean...there is a mag tube sensor and a humidity sensor.
Your mag tube is bad if there is more then 1 OHM showing. Be sure you  set your meter appropriately.

Tech Sheet for this model

[jacuze]

It is the Mag sensor, not the moisture sensor.  My meter was on the lowest ohms scale when I checked the magnetron, but I'll check again to make sure the leads made good contact.  I'll also check it with another meter.

My plan is to replace the mag sensor and then test the microwave. 

Thanks for the tech sheet and help.

Jacuze

[jacuze]

So, the thermostat came in and I replaced it.  Power to the microwave has been restored.

HOWEVER, I've still got a problem.  I put some water in the microwave to test it out.  After about two seconds I could hear the magnetron turn on and then I heard a extremely loud hum and crackle.  I quickly unplugged the microwave and took out the water.  I removed the waveguide cover from inside the microwave and I saw a quarter size burn mark that had been hidden by the cover.  While looking in the waveguide I see two vertical elements.  At the bottom of one of these elements is where the quarter size burn mark is.  To me it looks like the waveguide itself is bad and it has burned, almost through the inside panel of the microwave.

What chance is there that this can be fixed?  Is it worth replacing the waveguide.  If so, what about the quarter size burn mark in the top panel of the cavity of the microwave?

Here is a picture of what I see.

Any help would be appreciated.

[tgoods]

I think it's shot.  The waveguide is not replaceable. How old is it?  You have a 10 year warranty on the cavity for rust through. It's not technically rust but it's worth a shot. You might be able to get it replaced for free.

[jacuze]

The microwave has been used for less than a year, but was purchased over 1 year 1 month ago.  It sat in its box for a month and a few days before it was installed in a new construction home.

If you look through the side of the microwave, you can see three screws holding the three elements inside the waveguide.  The second screw, is loose and tilted to one side.  To me it looks like it didn't get tightened enough when the microwave was made and had worked itself loose over the year.  With the element out of place it messed with the "wave pattern" causing it to heat up at that location. 

I've seen in a few other places that people with the same series have had waveguide problems.  I hope I can get it replaced under warranty.  After all it did cost me $700 and didn't last a year of use.

Thanks for your help.