If you've got a Melitta brand burr coffee grinder like model MEBG8B but it won't grind anything, maybe you've got a stuck button. Here's how to fix it.
With our grinder, the buttons for 4,8,10,12 cups seemed to simply do nothing. It turns out that the shut-off button (top center) had jammed. Although I managed to get the button out of its cockeyed position, the grinder still didn't work.
Step 1: Remove the Beans
First, take off the lid from the bean reservoir and empty the beans into a bowl. We don't need those little buggers bouncing all over our floor!
Step 2: Remove the Controls
The five buttons (4,8,10,12 cup and shut-off) are all located on a single plastic-chrome piece on the front of the grinder. Using your fingernail, a very small screwdriver or other implement, insert it at the top in the seam between the chrome piece and the black plastic. Pry gently, and the entire control panel will probably pop out easily. It's attached with a few inches of insulated wire, so it won't entirely fall off, and there's no reason to worry about losing any pieces.
Step 3: Inspect the Buttons
A flashlight will help you get a better look at the buttons. Each "outer" button in turn pushes on a plastic post connected to a button on a circuit board, not too unlike the buttons in your computer's mouse. In my case, the posts are colored blue, and are sort of hidden inside a spring-like housing that keeps the outer button aligned with the post and provides the recoil on the button.
I looked at each of the four buttons at the bottom, and there was very little gap between the outer button and the inside posts. I could see the "grind" buttons working correctly as I pushed each of them. However, the shut-off button was indeed stuck! The post was sort of stuck in the down position.
Step 4: Gently Pop Up
Use your very small screwdriver to lift the head of the post. It may have a bit of a lip on it like mine did, in which case I was able to sort of lift the post out of its "stuck" position. If you think you've got it, compare it to the grind buttons again. Try out the action of the stop button. Does the post now depress AND rise again? Good!
Now, just like the cardinal rule of working on the internals of your computer: don't be overconfident; test your changes now, and don't be cocky, putting everything back together before you know for sure.
Plug the grinder in and push the "4-cup" grind button. It should buzz to life. Hit the shut-off button now, gently, so it doesn't jam.
Step 5: Replacing the Controls
It works! Now we just have to put things back together. Be sure that the circuit board portion of the controls fits inside the housing, and guide the controls straight in. There should be three little teeth that gently snap into place when you press on the panel.
Get back on that horse and brew some heaven!