One thing I've always found really ambiguous is whether "turning down" air conditioning means your reducing the energy supplied to the device so the room gets warmer, or if people are talking about the thermostat... so turning it down makes it colder.
I'm sure I've heard people use the phrase both ways, so... I thought I'd put it to the vote!
For the record, I think it makes more sense that "turning down" the air con means "make the room hotter"... Otherwise I'd say "turn the thermostat down" or "turn the temperature down"... But what do you think? Am I crazy?!