I just replaced the broken knob on the temperature control (been that way since I bought it). The knob is hard to turn, so much so that I fear I will break the knob again.

any ideas?

Two things could make it hard to turn-the water valve in the engine compartment or the damper on the passenger side of the console, On the damper, make sure it isn't blocked by the carpet etc. It is all the way up against the fire wall.