NOTE: This document replaces the previous text version
MICROWAVE OVEN DOOR SWITCH TESTING & REPLACEMENT
copyright 2004+ † updated February 3, 2017
William E. Miller, AS-EET
By utilizing information on this site, you agree to hold the owner harmless and blameless for any consequences arising from your decision to take apart or inspect your microwave oven. See the safety warnings linked belowbefore you proceed.
Please see my safety and disassembly pages here:
WHY DO MICROWAVE SWITCHES FAIL?
Besides normal aging and wear from use, what usually causes microwave door switches to fail is opening the door while the oven is cooking, instead of using the "STOP" pad on the control panel. Every time the door is opened during cooking, the switches get hit by an electrical arc that will cause them to fail in time. This phenomenon is called "inductive kickback."
My customers are always surprised to hear this, but it's something that most people do without thinking.
WARNING: Please, please be completely sure the oven is unplugged. Also, the microwave produces voltages over 3000V and can be instantly deadly, causing cardiac defibrillation. It is one of the most dangerous appliances if not handled properly.
Also, once you have the cover off, you may decide to identify the high voltage capacitor so you can discharge it before you begin work. For details on this and other VERY important safety precautions, see: http://microwavecontrol.com/safety.htm.
Next you'll need to find the switches. With the cover off, look around from the right side and they're located where the hooks on the door go into the chassis of the oven.
Here is a good diagram which represents a typical microwave, showing where they are: http://031d26d.namesecurehost.com/mwc/how_a_microwave_works.jpg
Often the switch will be held in place by a plastic retaining hook which may be beneath the switch and hard to see. A marked diagram is at: http://031d26d.namesecurehost.com/mwc/doorsw_release.jpg
There is an upper switch and a lower switch. There is also a switch in the middle, the "monitor" interlock. It does not need to be replaced unless it is shorted. It is wired differently than the other door switches. In addition, there may also be a separate door sensing switch. Door sensing switches will have thinner, colorful wires, while interlock switches have thicker wires, and they are usually black, white, and / or brown.
As you open & close the door, watch how the switches activate.
On the bad one, you'll probably see that its activator button (which is pushed by the door hook) is not moving out when the hook moves away from it.
Or you'll see that the switch body is warped, melted or charred.
You may have to take the switch apart to see the damage. See my rough video at http://www.youtube.com/watch?v=X9mEn5SPIW8
If you do end up replacing a switch, be very careful to replace the wires one at a time (like spark plug wires) and be sure each wire goes on the same terminal of the new switch the same
way it is on the old one. This is especially true for the center monitor interlock switch.
I strongly recommend that you do not remove the plastic piece(s) that the switches are mounted to. The plastic pieces are precisely aligned & mounted so that the door is held shut properly and will not emit microwave leakage while cooking. This can lead to arcing and fire. It's definitely best to remove the switch itself from its mount.
You may be able to get these standard door switches from local appliance parts stores, hardware stores, home improvement centers, Wal-Mart, etc. They will probably call them "micro switches".
Or we can send you a universal type with 1/4" terminals for $7.50 postpaid. See: http://microwavecontrol.com/switch_form.htm.
You can see a representative photo of such a switch here: http://031d26d.namesecurehost.com/mwc/doorswitch.jpg
ORDERING MICROWAVE OVEN PARTS
See my parts page at http://microwavecontrol.com/parts.htm.
Please visit my Web site and e-mail me. It's best to e-mail instead of calling, because that way I can e-mail you pictures, links, and files as needed.