Model #MT4110SPQ0, this counter top microwave had been working just fine for the customer, but when she went to use it last, the door wouldn't open. Any amount of button pushing or coaxing seemed to have little affect on the fact this door was not going to open. We all tend to rely on the convenience of our microwaves these days, and to this customer, getting it fixed was important enough to call for help.
The door latch mechanism on many microwaves are often simple in design to keep things inexpensive to produce and to make them reliable to use. The important part of the latch itself is a microwave part called an interlock assembly which contains the switches used to ensure the microwave door is closed before the magnetron begins to operate. This assembly is setup in such a way to prevent tampering from the outside and allowing the unit to function with the door open. The usual result of this kind of switch manipulation will be a dead microwave and a blown monitor fuse.
Depending on the make and design (counter top or over the range) of the microwave, the door mechanism may look a little different, but how they work is often very similar in that a push button actuates a release arm to push the door latch assembly free of the catch. How this is done, as I said, will change depending on the design, but the manufactures try and keep it simple for the reasons listed above.
On this microwave, I started by removing the cover which requires the use of a #20 Torx bit screwdriver (used to prevent just anybody from getting inside) and setting it aside. With the cover removed, most everything can be accessed and this is where the safety speech comes in. Microwaves use very high voltage during operation and these voltages can still be present with the unit unplugged. If you choose to do any work on your microwave, it is important to discharge the capacitor (see my Microwave Servicing Disclaimer post) before touching anything.
With the microwave unplugged and the capacitor discharged, just to be safe, I actuated the door release to get an idea of what may be causing the problem. Pushing the release button would actuate the lever, but not enough to allow the latches to come free from the catch. Acting like the button just wasn't pushing enough, I decided to remove the button to have a look.
The reason I did this is it is not uncommon for one of the tabs to break loose and become stuck between the button and the recess of the control panel. When this occurs, the button cannot fully depress resulting in the failure we have here. After taking a look at the button, sure enough, I found a broken tab (sorry no photo, just trust me on this) that was causing the whole problem. I reassembled the panel with a new button with all the tabs intact, and tried to open the door again. With the new button in place, the release arm could easily push the latch high enough to come free from the interlock assembly. The cover was reinstalled and the unit was returned to the counter top where a push of the button, was all that was needed to open the door. Just like before.
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Thoughts and commentary about appliance repair topics including common failures and repairs, plus links to frequently used parts, industry news, along with information to help you better understand your appliances. Resources available for the technical professional and the do-it-yourselfer.
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