MGB Heater question

[Ryan Watson <rswatson@nyx.nyx.net>]

Hi there,
My Heater (in a 1979 B) seems to have three contols:
1. Fan switch for blowing air
2. Interior/defrost knob for directing the air
3. Off-warm-hot knob presumeably to control the temperature.
But with the #1 on and #3 off, I still get warm air.
My question is: Is this the nature of the beast to have a choice of hot, 
hotter, and hottest or is something wrong?
I would like to be able to blow cool air through the de-misters, if possible.

Thanks,
Ryan