Apparently this is a well known issue with Accord a/c temperature
control knob.

The knob turns a cable which is connected to some sort of valve to mix
the hot air from the heater to control the a/c temperature. Since the
valve/cable assembly is getting so sticky that it requires a lot of
force to turn it which cause the knob to crack into two halves. I have
gone through several knobs already and now I have a small 'metal'
crescent wrench to turn the shaft. (May be Honda should give you a free
crescent wrench with each car purchased).

Now the question: Is there a way to make this assembly back to virgin
state? Is it the cable needing some grease or the valve needed to be
replaced or cleaned?

Thank you,