It sounds as if the switch itself needs power for the 'timer' function,
hence the need for a white wire (common) to attach to the whites (commons)
in the box These would not have been attached to the old switch, rather
would have probably been joined with a wirenut in the back of the box.
EXCEPT - since you say you have a white that is bare, that was probably
connected to the old switch, I'm thinking your hot came into the light and
what you have in your switch box is simply a drop down from the light. That
is, you don't really have a common to connect to - that's only available in
the box at the ceiling where it connects to the light.

Did you only have a black and a white connecting to the old switch? Did the
white have any kind of marking on it (tape or paint) to indicate it was a
hot and not a common?

My guess is that with your configuration you may not be able to use your new
switch.

wrote in message
ups.com...
Hi all,

Sorry if this is really trivial, or has asked before, but I can't seem
to find an answer.

I just bought a new light switch for the laundry room in the basement.
It is a Leviton brand which has a bunch of buttons to give you a
predefined amount of "on" time for the light - i.e. you hit the "10"
button for 10 minutes of light.

The switch has 4 wires: Black, white, green, blue. The old basic
switch has 2 wires - black and white. The wiring diagram from Leviton
shows multiple wires coming in from the top and bottom of the switch
box, and how to wire things appropriately.

My old switch has only the two wires: black and a white.

I assume the new switch green goes to the grounding screw on the box.
I also assume the white should be joined to the white, and the black to
the black, each through Marrs connectors.

What do I do with the blue. I've tried a couple of things (joining it
in with the blacks) which powers the switch properly (it has LEDs that
show which timer setting is in use) but the light doesn't go on - which
is really the whole point of a switch....

What should I be doing?

TIA,

Dave