How do you switch red brick abilities in Lego Harry Potter years 1-4 for ds when hit the L button it just takes to inventory?

You are correct! The L button on the Nintendo DS version of Lego Harry Potter Years 1-4 is *not* used to switch red brick abilities.

Here's how you actually switch between abilities:

* Touchscreen: Tap the ability icon you want to use. It's usually the icon at the bottom left of the screen.

* Stylus: Select the ability icon with the stylus and tap on it.

The L button is used to open the inventory, as you mentioned.

Let me know if you have any other questions about the game!