[Engine-Ear]

We have a mid-level microwave (brand-labeled as a GE) that we got new about 6 years ago. It doesn't get much use other than heating water, left-overs or defrosting stuff.

Well now the damn thing has taken to tripping the breaker when the door is opened. In fact, I confirmed that if I plug it in with the door open it trips the breaker.

To my way of thinking, the AC Line (hot) is getting shorted either to neutral or ground by a switch that changes state after the door is open.

Question: Could Neutral be getting shorted to ground and causing a breaker trip? (I don't think this circuit has a GFCI outlet on it.)

There are at least two switches actuated by pressing the door-open button (which is clunky, plastic-ey, Rube-Goldberg affair) that actuates the switches elsewhere behind the display button panel.

What I think I will try to do is, with the door open, look for a short-circuit between L-N, L-G or N-G. Then I will disconnect one switch at a time and look for the short to go away.

...Does that approach make sense? Of course there are semiconductors and ICs in there and I don't know enough about these to know if there is another, common culprit.

...Big picture is, while I am NOT an eco-nut, it simply grinds my gears to see this machine go into the trash (or recycle it, which isn't any better for Bambi or the planet, given the amount of energy that goes into recycling). Plus I don't have the money to replace it with yet another Chinese-made appliance.

As always, I welcome relevant input!

[6TEE8GTO]

Your monitor switch is shorted. There are a series of switches that work together so that there is no way to have the door open when the high voltage section operational. That would be very bad, so if one of the switches were to short closed, the next time you open the door, yes the fuse blows. Check the micro switches and PLEASE be careful, the hi-volt capacitor can zap you badly even with the unit unplugged....

[6TEE8GTO]

Just FYI, the switches will be marked with COM, (common) NO (normally open) and NC (normally closed), put one of your ohm meter leads on COM and then if the switch plunger is NOT depressed, you should have continuity from COM to NC, if the plunger is DEPRESSED, you should have continuity from COM to NO...

[Engine-Ear]

First off, that's useful info, 6TT8GTO. Thanks! I am also thinking that it's the monitor switch, BTW.

As it turns out, there are four different switches that all attach to a modular plastic tray. They are all small, low-current, plunger/lever-actuator with plastic housings and look like cheap junk.

I will call an appliance parts place in Milwaukee and see whether separate switches are available or if I have to/can buy the whole switch group on the bracket.

So instead of actually working for the last few hours, I have been trying to isolate variables on this thing ... I verified that it is the L-N is what's shorting out when the door is opened. The N-G isolation does not change when the door is opened. I also bypassed the ground lead on the plug and repeated the failure mode.

[AROWHED]

Gotta wonder how that unit ever passed UL.

[6TEE8GTO]

What's happening is not unusual at all. Think about it, what if all they had was a single door switch, like a dryer or a dishwasher? If the switch were to weld shut (contacts stick together) and you opened the door while the unit was still running (which people do all the time) you would get a face full of RF... Another thing is if a kid tried to stick a pencil or something in the hole for the switch and turn the unit on? (you know the kind, future Darwin award winner) Those 4 switches you speak of are a series of switches designed to work in a specific sequence, and if one of them gets out of sync with the others, it won't fire the high voltage transformer, and if the monitor switch sticks closed, POW, fuse is SUPPOSED to blow and force you to have the unit serviced. Also note if you remove any switch from the plastic holder, and replace them, that's ok, but do NOT disturb that plastic bracket's adjustment, unless you have a microwave leakage detector to verify if you have any RF leakage. If it matters any, I used to own a microwave/tv/VCR shop in Glendale back in the 90's, but the prices of all three started to drop rapidly and got to where the things are throw-away if they are counter top units. Even the over-the-range units are getting so cheap that people hardly repair them. Back in the day GE actually made their microwaves.
Now 90% of all microwaves built are made by either Samsung, Daewoo or Sharp, and re-badged....

[Engine-Ear]

Great post, Greg.

[sonjaab]

For what its prob. gonna cost for the switches (if they still make them)
not to mention your time it would prob. be cheaper to just toss the
old micro for a new one.
Heck my new over the range hitachi nuke was only $125 at the local
big box store.

[Engine-Ear]

You are right, sonjaab.

But as I said above, while I am not an eco-nut, putting in a little time and $ to return this otherwise-functional appliance to service seems like far less energy invested than the alternative ending for this item.

By "the alternative", I mean the indirect energy consumed by the garbage truck / material sorting facility / glass recycling facility / metals recycling facility / oil drum-bound circuit boards that will get sealed up and buried (and all the infrastructure that does that), etc. etc. ...that is IF it gets "recycled". If it doesn't, just goes into some landfill as is.