Climate Control not blowing very cold

When I set my climate control to 'Lo' it no longer blows very cold. Until recently - not sure when exactly - it would quite cold, almost icy but now it feels like it is just blowing air through. I haven't tried so see what happens if I turn the temp up (only just occurred to me) but is there anything I can check to see if it working properly or if there are any obvious signs that something in particular is wrong?

That's what my resident car expert (a housemate) told me but I wanted to get as many other opinions as well, just in case /ubbthreads/images/graemlins/wink.gif