microwave microswitch

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Hi Gents, Well the microwave stopped working over the holiday.
(Two year old Cuisinart)
(Insert rant here about security screws.. torx with the pin in the center.)
After opening it up I found that the main door micro switch was no good. The warning on the inside says to only replace with other KW3A switches. Here’s a picture of what it looks like.

http://www.made-in-china.com/showro...ailcMCmWhZrZGYo/China-Micro-Switch-KW3A-.html

125V, 16A. Only has NO contact populated.

I’m looking for some place to order this is the US. There are similar looking switches made by honeywell and sold by mouser or newark.
These are V7 series. V7-6c17d8 14 ozf of force
or V7-1c17d8 5.6 ozf of force.
(only speced to 15 amps.. but should be fine.)
I figure I should order a handful of them since there are *three* switches in the door.
So first what’s an ozf? is it an ounce? I guess I can pull one of the working switches and measure how much force it takes to close it.

Here’s a link to newark.
http://www.newark.com/honeywell-s-c...t/dp/39B3001?MER=PPSO_N_C_EverywhereElse_None

any other advise is welcome.
(Hey I'm still searching for specs on the KW3A switch... like life time andcontact force.)

George H.

 

[N_Cook]

Hi Gents, Well the microwave stopped working over the holiday.
(Two year old Cuisinart)
(Insert rant here about security screws.. torx with the pin in the center.)
After opening it up I found that the main door micro switch was no good. The warning on the inside says to only replace with other KW3A switches. Here’s a picture of what it looks like.

http://www.made-in-china.com/showro...ailcMCmWhZrZGYo/China-Micro-Switch-KW3A-.html

125V, 16A. Only has NO contact populated.

I’m looking for some place to order this is the US. There are similar looking switches made by honeywell and sold by mouser or newark.
These are V7 series. V7-6c17d8 14 ozf of force
or V7-1c17d8 5.6 ozf of force.
(only speced to 15 amps.. but should be fine.)
I figure I should order a handful of them since there are *three* switches in the door.
So first what’s an ozf? is it an ounce? I guess I can pull one of the working switches and measure how much force it takes to close it.

Here’s a link to newark.
http://www.newark.com/honeywell-s-c...t/dp/39B3001?MER=PPSO_N_C_EverywhereElse_None

any other advise is welcome.
(Hey I'm still searching for specs on the KW3A switch... like life time and contact force.)

George H.

seems to go back to the days of slugs, ergs and all that antedeluvian
stuff. Like pound-force, presumably ounce-force

 

[[email protected]]

(Two year old Cuisinart)

*People's Shining Microwave Factory #7 with a Cuisinart sticker on it.

Standard warning: There can be enough juice in the big capacitor to zap
you dead, even if the oven is unplugged. There's also a lot of RF
floating around, sharp edges, etc. Be careful.
http://www.repairfaq.org/sam/micfaq.htm#micsaf

(Insert rant here about security screws.. torx with the pin in the
center.)

For household stuff, Hazard Fraught Tool's $6 security bit set comes
in pretty handy. Not what you'd use for production, but fine if you
need it a couple of times a month. Chain hardware stores like Ace
and True Value tend to carry this same set as well.
http://www.harborfreight.com/33-piece-security-bit-set-68459.html

After opening it up I found that the main door micro switch was no
good.

There are usually three microswitches. One of them opens the 120 V
line from the wall, like you would expect. One of them switches a
low-voltage circuit to the control board. One of them *shorts* the
120 V line on purpose, blowing the fuse in the microwave, if the other
switches operate in the wrong order. So... check the main fuse as
well. Also look at the plastic assembly that interfaces between the
door latch prongs, the door open button (if equipped), and the
microswitches; if this plastic cracks or gets bent, it can either push
too hard on the switches or not push them at all.

I figure I should order a handful of them since there are *three*
switches in the door.

They may not all be exactly the same. Sometimes the one that goes to
the logic board has both NC and NO contacts.

So first what?s an ozf? is it an ounce?

Ounce force. (As distinguished from ounce mass.) 1 ozf is about
0.278 N . http://en.wikipedia.org/wiki/Ounce#Ounce-force

any other advise is welcome.
http://www.repairfaq.org/sam/micfaq.htm#micintrlk
http://www.repairfaq.org/sam/micfaq.htm#mictstris
http://www.repairfaq.org/sam/micfaq.htm#micsrmop

(Hey I'm still searching for specs on the KW3A switch... like life
time

Ten minutes longer than the warranty on the microwave.

and contact force.)

This Taiwanese vendor has several flavors of KW3A switch, with a good
amount of specs on each one:
http://switchtech.com.tw/upload/201162285428410.pdf

Standard disclaimers apply: I don't get money or other consideration
from any companies mentioned.

Matt Roberds

 

[[email protected]]

*People's Shining Microwave Factory #7 with a Cuisinart sticker on it.



Standard warning: There can be enough juice in the big capacitor to zap

you dead, even if the oven is unplugged. There's also a lot of RF

floating around, sharp edges, etc. Be careful.

http://www.repairfaq.org/sam/micfaq.htm#micsaf







For household stuff, Hazard Fraught Tool's $6 security bit set comes

in pretty handy. Not what you'd use for production, but fine if you

need it a couple of times a month. Chain hardware stores like Ace

and True Value tend to carry this same set as well.

http://www.harborfreight.com/33-piece-security-bit-set-68459.html







There are usually three microswitches. One of them opens the 120 V

line from the wall, like you would expect. One of them switches a

low-voltage circuit to the control board. One of them *shorts* the

120 V line on purpose, blowing the fuse in the microwave, if the other

switches operate in the wrong order. So... check the main fuse as

well. Also look at the plastic assembly that interfaces between the

door latch prongs, the door open button (if equipped), and the

microswitches; if this plastic cracks or gets bent, it can either push

too hard on the switches or not push them at all.







They may not all be exactly the same. Sometimes the one that goes to

the logic board has both NC and NO contacts.






Ounce force. (As distinguished from ounce mass.) 1 ozf is about

0.278 N . http://en.wikipedia.org/wiki/Ounce#Ounce-force







Ten minutes longer than the warranty on the microwave.






This Taiwanese vendor has several flavors of KW3A switch, with a good

amount of specs on each one:

http://switchtech.com.tw/upload/201162285428410.pdf



Standard disclaimers apply: I don't get money or other consideration

from any companies mentioned.



Matt Roberds

Thanks for the nice response Matt. I did short the cap before poking around inside. Once I found the bad switch I shorted the spade lugs and the microwave ran just fine... so no other damage.
I measured the plunger force last night. ~5 - 6 oz. So I'm going to get some of the honeywell switches. They list a electrical life of 100k operations vs 50k for the specs I found for the KW3A. I was thinking that as well as the average time to failure it'd be nice if they also included the standard deviation. (I guess that's too much to ask.)

George H.