Any microwave oven experts?

S

Snagglefoot

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My 11 year oil microwave popped the 20 amp dedicated breaker. It also looks like it blew its internal fuse. To give it the Hail Mary I’m willing to replace the fuse and also have a second one ready to go. The capacitor is easily accessible from the front of this over-the-stove Whirlpool microwave so if it pops the breaker again, I plan to replace the capacitor. I’m comfortable discharging them. There were no weird sounds prior to the breaker going. It had just finished a 10 minute session on high and it counted down to zero and displayed “End”. When Mrs. Snagglefoot opened the door the microwave’s lights went out. The 20 amp breaker downstairs had popped.

Does anyone else have any additional thoughts? My local repair guy typically charges 50% of a new appliance when he fixes an old one. Definitely I would just buy a new one rather than take it to him. Any other easily repaired faults? Thanks. Snag

Here’s the general type of capacitor it has. I have to pull it to get a match.

027A77CF-D1CB-4EC1-8666-1C006C03D937.png
 
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Not a repair guy but I'd probably shotgun the diode and cap. I know I had mine repaired once, and want to say the repair guy "always" did diode and cap. But it didn't trip a breaker, it just plain didn't work (but too many years now to remember what actually died).
 
Some microwaves have a "booby trap" interlock switch which will make it trip the breaker / blow the fuse if someone attempts to make the microwave work (with the door open) by jamming something into the interlock switches. This switch could be the problem here.

That capacitor you think is the problem is only going to cause a blown fuse / tripped breaker if it fails (shorts out) while the magnetron is powered up.

That isn't the case after the microwave has completed the cycle.

Since it blew the fuse seemingly as soon as your wife opened the door, I think the problem is with the interlock switches, NOT any of the high voltage components. They aren't (shouldn't be) getting any power after the cycle has ended (see edit below).

EDIT: Another possibility is that the relay which controls the power to the magnetron has welded closed, the magnetron was still powered up when your wife opened the door, and the "booby trap" switch did it's job and blew the fuse.
 
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Since it went out right when your wife opened the door: It might be worth checking the door switches. My microwave went out a few years ago and I found a shorted door switch(which caused a thermal fuse inside to pop). No breaker tripped when this happened though.
 
I have a lowes whirlpool overhead microwave. I just had to do the door switches on it.

There is actually a set of six different switches, supposingly to fit most of the microwaves on the market. You buy the kit on amazon, you use the switches that fit your unit, and throw the rest away.

I think it was like 15 bucks but it solved the problem of mine flipping the breaker.

Watch a few youtube videos, you need a few torx bits and some dillying around but it takes about 15 minutes.
 
I agree, test the door switches first.
There are usually 2 or 3 of them in a microwave.
There are 2 type: Normally Open and Normally Closed switches.
 
Yes, getting convinced about the door switches. Now it would require some disassembly instead of easily reaching the capacitor. Given the age of it, I’ll probably pull it down and look for a similar one with identical vent outlets. Thanks for all the input. Snag
 
At the risk of jinxing myself, I have had experience with four Panasonic microwave ovens, two of which are over 20 years old, and they all have functioned trouble free. The basic design does not appear to have changed over the last 20 years.
 
All I know is be careful replacing the fuse… I did that once and it worked, for about 10 seconds then blew the fuse again, except this time it also vaporized (I’m not kidding, they were just gone) the thicker power traces on the PCB with a very loud POP! and smell of escaping magic smoke.
 
Check the cap with an ohm meter. If it's not shorted, I doubt that's what is blowing the fuses. I would scrap the microwave and get a new one. Door switches will not cause excess current draw and blow a fuse. I had them go bad before and never blew fuses. Fuses blow because something caused it like a short, they do not wear out.
 
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Get the model and serial number of the oven. Go to a website like this to confirm the capacitor part number and/or specs:

Appliance Parts Pros.com Discount Appliance Parts – Since 1999

Over 2.1 million appliance parts in stock, ship the same day. Free tech support. 365 days to return any part. Wholesale prices on all appliance parts. Open 7 AM until 8 PM Eastern Time, 6 days per week
www.appliancepartspros.com www.appliancepartspros.com

Once you have the info, you can shop price.

Over the range microwave ovens can be pricy. It's one reason I twice repaired the one (GE) over our range. The only downside is getting it back onto the wall. It's very awkward trying to lift it onto the wall plate when there's cabinets on both sides.

I shotgunned the repair both times - magnatron, capacitor and diode. Symptoms - 1) no heat. No strange noises; 2) arcing noises.

A potato fire finally did it in. I stuck with GE since I have external exhaust ducting; GE has maintained their ducting connection design for the past 20 years so installation was a basic R&R. $340 for the oven, $150 for installation (I didn't want to deal with it). Purchased from a local appliance dealer, installed by a local handyman. Big box pricing wasn't any better.

FWIW, I had the condenser fan motor starter capacitor go out twice on the house AC unit. Both times, the capacitor was visibly swelled.
 
Lubener said:
Check the cap with an ohm meter. If it's not shorted, I doubt that's what is blowing the fuses. I would scrap the microwave and get a new one. Door switches will not cause excess current draw and blow a fuse. I had them go bad before and never blew fuses. Fuses blow because something caused it like a short, they do not wear out.
Click to expand...

1687128112039.jpg
 
Lubener said:
Check the cap with an ohm meter. If it's not shorted, I doubt that's what is blowing the fuses. I would scrap the microwave and get a new one. Door switches will not cause excess current draw and blow a fuse. I had them go bad before and never blew fuses. Fuses blow because something caused it like a short, they do not wear out.
Click to expand...
Shorts are caused when switches mechanically fail in the microwave. This is extremely common.

mastersamuraitech.com

How does the Monitor Switch in a Microwave Work? - The Master Samurai Tech Academy

Here’s a GE microwave schematic. There’s a lot of typical microwave stuff going on here, but we’re going to focus in on one component today: the monitor switch. What exactly... Read more »
mastersamuraitech.com mastersamuraitech.com
 
Caps rarely go bad, same with diodes. We always changed both when doing a mag job for a one and done with warranty work. Especially on over the range units.
Look at the spades on the door switches. Black discoloration on them are signs of heat from weak contacts inside. Welded switch contacts are common. Most of those switches are only rated at 15 amps and opening the door while mag is running stresses those cheap switches. Board relays can stick, not common but it happens.
 
Now for the rest of the story. I replaced the 20 Amp fuse and plugged in the microwave and flipped the breaker to on. The power came on. I then opened the door and whamo, blown fuse and breaker. Yes, looks like the interlock. Enough for me. I purchased a new one. Thanks everyone for you kind interest and advice.
 
k1xv said:
At the risk of jinxing myself, I have had experience with four Panasonic microwave ovens, two of which are over 20 years old, and they all have functioned trouble free. The basic design does not appear to have changed over the last 20 years.
Click to expand...
My made in USA Tappan was made in 1989 and still works. It's complete with a wood grain finish.
 
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