Hello all,

Hopefully someone can help me with this microwave issue.
Microwave is a Magic Chef over the range model number MCO153S.

The issue:
The oven will turn off/power down after extended use (10-15 minutes). No lights no nothing for about 15 minutes and then it will power back on. I can then reset the clock and use the oven again. It seems to be a thermal issue of some sort because it will work after a cooling period.
Recently I was able to run the oven with the control panel off to listen and watch as it shuts down.
What I noted was that the oven will make a different kind of low hum noise and the mag cooling fan will slow slightly (Not much) as if the unit is drawing a lot of current. About 10 or 15 seconds later it shuts down.

What I have done so far:
Pulled the oven and checked for debris or any blockage for the external venting.
Checked the internal inline fuse to make sure it was secure and had good contacts. The contacts for this fuse actually fit right over the fuse ends and were in good shape with no evidence of heating. The magnetron itself does not appear to be overheated other then some brownish grease stains on the very edges of the plates.

Also checked the resistance on the thermal switches for the following:
Vent Thermostat = .2 - .3 ohms
Bottom Thermal Cut Out = open
Magnetron Thermostat = .2 - .3 ohms

Then I pulled the magnetron thermostat and applied heat with my heat gun and watched the temp with an IR temp sensor. This would go from .2 - .3 ohms to open at about 150F degrees.

What I may do next:
Run the oven with the control panel off until it fails and monitor the magnetron case and sensor with the IR temp gun (I could also hook a meter up to it). Then, depending on what I see, I can pull the case off and check cavity thermostat.


Questions:
Could a failing or partially open sensor cause this issue?
What type of temperature could I expect to see on the magnetron during normal operation (With the control panel not in place)?
Any recommendations?

Thank you magician59!!

For some reason I was thinking that this was a normally open switch.:eek:

I'm feeling a bit foolish, but I am thankful for your quick response. I will go get another switch and promise to take a better look at my schematics in the future.:D

Thanks again.