I have an old house. The previous owner redid the attic into a bedroom.

He has a Switch at the bottom of the stairs, it runs to the attic, the
to an outlet.

This switch controls a Fan, and top outlets of two wall outlets, then
passes power on to the bottom outlets always hot.

I want to install another switch. I have 12/3 wiring.

does this make sense?

Switch - 12/3 wiring - Fan - Top Outlets
Power through switch not controlling rest of circuit.

Does't make sense to me, I'm lost.

Abraham

from buffalo ny: the source of the power isn't the switch if the
switchbox has only two wires, they may be just opening the hot circuit.
the hot attic outlets may be separately fed unless there are more
working wires in the switchbox.
the outlet bottoms have constant unswitched power suggests that the
link between the upper and lower of the duplex outlets has been
separated to allow you to turn a lamp on or off separately from a
constantly powered device like a clock radio.
who: you and a neighbor with a flashlight and a voltmeter and basic
tools
what: do you want to control with another switch?
whe does the new switch need to be located?
when: you turn on/off the switch will it be a 3-way switch setup for
the existing outlets to be controlled from the top of the stairs for
example?
why: what wattage device do you plan to control will determine what
wiring or parts are required.
how:
see pictures at:
http://www.selfhelpandmore.com/homew...ures/index.htm
see basic info at:
http://www.faqs.org/faqs/electrical-wiring/part1/
and ask us for more info if you get stuck.
read up on 3 way switched, 4 way switched circuits.

select the electrical project and see the helpful illustration at:
http://www.selfhelpandmore.com/switchoutlet/