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.
For tips and questions, leave a comment or join www.robotreviews.com
Step 1: Intro to Disassembly
All Bumper and Cover retaining screws must be removed before attempting dismount of either subassembly. The two subassemblies must mechanically disengage Chassis fittings as a set; at least for the first few millimeters of movement.
Steps in HoB apply to the following Discovery models, in which the Handle is mounted on the Bumper and interleaves with the Cover:
Roomba-Discovery, #4210Roomba-Discovery Replacement, #4211
Roomba-Discovery SE, #4220Roomba-Scheduler, #4230
Note: We have not had hands-on experience with the Discovery SE, or Scheduler models, but those bots are considered mechanically identical to the #4210 Discovery, which is known to reward owners when the HoB process is used.
Models #4210 and #4220 that were produced prior to, roughly, mid-2005, came with some removable parts that are called "Fender Skirts" in these documents. It can be useful for an owner to recognize whether his Roomba has Fender Skirts, because their presence provides much easier access to the drive-wheels; and also explains why two very long screws are used just forward of the drive- wheels. The image below has pointers to the joint features which indicate presence of a Skirt.
A Fender-Skirt is a removable panel which spans the distance between those joints. Roomba-owners who purchased either of these Discovery models after mid-2005 should inspect the left and right sides of their bot to see if "Fender Skirts" exist on their particular unit. If no Skirt-joints are visible, no Skirts exist on that Roomba.