Blown Fuse: Don’t JUST fix what’s broke

Closed the Microwave door and… ZAP! A bright blue flash from the lower door latch, loss of all power, casualty. Check the breaker panel, and nothing’s tripped. Crumb. On the microwave, well, it’s just a blown fuse.

(GIF Credit)

Obviously, this 20Amp fuse took issue with the current draw. The fuse was heated so rapidly that it exploded the glass enclosure. Just a tad beyond 20Amps.

It’s time to upgrade, right?

From Equifactor® and TapRooT®, there’s probably more to the story. Let’s go find what caused the high current that led to the blown fuse. Play with a few switches in the latch seat, and find where the blue flash came from.

The switch didn’t click when I pressed the white button; it flexed.

Ok, so replace the switch, and off we go.

Right?

Nope. Replaced the switch and the blown fuse; fuse EXPLODES again.

Just a quick search and you can find it’s probably a failure in the…

Magnetron.

Great basic explanation here: https://www.explainthatstuff.com/how-magnetrons-work.html

Magnetron replacement warnings are rivaled only by those of garage door springs. Let’s not die over a $100 machine, lads. I know what happened now, but proving how the equipment failed is ONLY HALF THE PROCESS!

Eventually, the root cause tree questions led me to select Equipment Difficulty – Tolerable Failure category. Not random, not statistical, not “normal wear and tear” but definite, justifiable TOLERABLE FAILURE.

For anything more complicated or expensive than a microwave, Equifactor® is where you go. Especially in higher-stakes troubleshooting, you need a structured plan and strategy to prove how the equipment failed, then to investigate the root causes of that failure.

Get to any Equifactor® course to learn the art of complex, systematic troubleshooting to prove how your equipment failed, the missing best practices that allowed it to fail, and how we correct it.

For the pinnacle experience of the TapRooT® equipment world, get to the Maintenance and Reliability Best Practice Learning Track at the TapRooT® Global Summit on Root Cause Analysis.