Ok, my central air doesn't work, my central heat does. Took the panel off
the unit and found out:

Blue (Rc) - Yellow = 0 volts
Red (Rh) - White = 24 volts AC

The furnace is new, put in last year by a professional installer. The AC is
old, and may or may not have problems of its own (I've not had the house
long enough to need it)

My pal Google tells me there may be a fuse on the board, which I will check
tomorrow. But wouldn't a blown fuse keep anything from working? If the
fuse is good, I'm guessing the board is bad, but with it being new that
seems unlikely. Anything else I should check?

Thanks.