Is your Roomba 400 not charging? When you plug it in, does it light up but when you press the button you get no response? Here's the disassembly guide as well as a guide to fixing the U2/U4 Problem. This will also give you a chance to clean out all the Dust that builds up inside, you could clean out the inside of the brushdeck and preform the sealed bearings mod, and much more. In addition, once you open it up, you can see and clean all of the dust balls inside. Literally, the inside is usually PACKED with dust. That dust is harmful to the Roombas in many ways.
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