GE Monogram Microwave ZE2160SF01 magnetron thermal fuse blown and burned

[esliu]

Hello all,

I have a GE Monogram ZE2160SF01 Microwave from 2005 that is operating but not heating food.  I don't think the magnetron is powering on (I don't see the lights dim, I don't hear the magnetron hum).

I have repaired this microwave twice before.  The first time in 2017 was because the door interlock switches failed.  The second time last year, the thermal fuse blew.  This time, the other thermal fuse (which I replaced at the same time as the other thermal fuse) has blown and the wire connector is charred/melted.  This thermal fuse is supposed to open at 248 degrees F and is situated on top of the magnetron. The connector that burned is the one coming directly off the transformer to the thermal fuse.

If you look at the wiring diagram, you see that this "M.G.T. Sensor" sit off terminal 1 of the high-voltage transformer. I'm pretty confused as to how everything else seems to function when this fuse is open, because the wiring diagram seems to imply that this is a pretty populated loop (assuming all the red wires are the same circuit).

Anyhow, I could just replace the thermal fuse again but that certainly doesn't seem to me like it would solve the problem, and that charred terminal (see photos) has me worried.  I took the magnetron off and visual inspection seemed fine. I tested resistance between the terminals on the magnetron and it seemed fine at .2 ohms.

Any ideas on what I should investigate next?  I can't see anything else obviously wrong through visual inspection.  Thank you in advance for any help!

[Quick]

@esliu

Maybe you just had a bad connection at the cut out.

The bad connection produced enough heat to trip the thermal fuse?

Replace the fuse and that burnt connector with a good tight connection.

Edited September 22, 2019 by Quick
Forgot to catch eslius attention

[esliu]

Thanks for your response!

Hmm, that seems unlikely but sure, possibly? I'll order the thermal fuse and replace the connector.  Does anyone know a source for these white, boxy plastic connectors? I have standard blade connectors but these seem specific to this application...not sure how much that matters, but I like to be as close to original as possible.

[Vance R]

I would recommend a high temp terminal, doesn't need to be insulated. . Cut the wire back to clean copper and crimp tight. Fit the connector for a snuggle fit on to the terminal of tco. The current draw is somewhere around  12 to 14 amps. Because of the high current draw any loose connection will generate heat.

[David Jero]

This was VERY common with this. During manufacturing the connector wasn't slipped o the terminal correctly. The male and female wasn't inserted correctly. This causes a weak connection and therefore burnt the connector over time. I must have repaired 100's of these.  Do yourself a favor and replace the thermostat while you are at it.  Most of the time that heat burns the terminal right into the connector.  Make sure you make the connections very tight and this will never happen again. Use a quality spade connector as well.