NotoriousREV

I have a MY93 WRX with A/C and the temperature controller has 20 - 30 marked on it, which I assumed to be degrees celsius, but instead it seems to be some Japanese temerature scale which is relative some mystical force.

With A/C switched off:

Set it to 22, it's comfortable then suddenly starts to blow hot air, so you turn it down to 21, still hot, so you turn it to 20 and (with the fan set to auto) it starts a tornado of cold air, so you turn it back to 21 and it's still cold, so back to 22 and the fan slows down a bit but it's still cold so in a fit of rage you turn it to 25 and it starts to be comfortable again, if a little on the warm side so you give up and open the window.

With A/C on it's fine, but off it's a night mare. Is it just mine or are they all the same or is there a simple fix?