Coffee time!

There's a room with a 1cupper coffee maker in it.
The door to the room is closed.

There are 3 switches on the wall outside the room next to the door.
One of them is connected to the coffee maker. All 3 switches are "off".

You can only have one switch "on" at a time
and you may open the door and go in only once.

How can you determine which switch is connected to the coffee maker?

Turn on switch 2.
Wait a coupla minutes.
Turn off switch 2.
Turn on switch 3.

Enter room and feel coffee machine.

Cold = Switch 1
Warm = Switch 2
Hot (on) = Switch 3

Right...or look at coffee cup:
filled? switch 2
being filled? switch 3
else switch 3