Brush Deck Height Adjustment String

The following are instructions for inspecting the brush deck height adjustment string. Please note that this is a discovery series Roomba.

Steps

Step 1: Remove the dirt bin.

Roomba 4160 shown for demonstration

Step 2: Prop the Roomba up on its bumber so that the brushes are facing you.

Step 3: Peer into the opening between the top cover (blue in picture) and the brush deck (yellow in picture)

The string is circled in red

Step 4: Look towards the left side of the brush deck for the string. You should be able to get it to bend by moving the brush deck.

If there is no height adjustment string, or it is broken, you must install one.

What Does It Do

iRobot claims that Roomba will “Automatically transition between different floor types.” It does this with the brush deck height adjustment string. If resistance against the brushes turning increases, the entire motor itself turns, rolling up the string. Because the motor is attached to the brush deck, it pulls the entire assembly upwards. So if Roomba climbs onto a carpet, the entire brush assembly will lift up to reduce the friction between the brushes and the floor. If the string is broken, the brush deck will be unable to lift if the robot goes onto a rougher floor surface.