After you visit the land of the living you get access to the tube switcher room (right before the main entrance doors).
The repair demon complains that the boys upstairs throw their beer bottles into the tube system breaking it. It is a delicate machinery.
This is the low-spoiler guide for "Opening the tube switcher door" puzzle in Grim Fandango. Unlike in normal walkthrough, you get gradual hints on how to solve the puzzle. Click the big button below to see your first hint. If the hint contains a spoiler, you will be warned about it before clicking.