they dont seem to pull off because i have to pull mine in order to turn on everything, so i dont think that my would just pull off because then i would never be able to turn anything on
For the fan control switch and wiper switch (potentiometers) that pulled/fell off the shafts in 'Betty' I just went down to Rat Shack and found a pair of matching knobs with set screws, no problems since.
The switch knobs have a spring washer type thing that will depress and release. Those with cables attached were kinda fused onto the shafts and normally just fall off.
Maybe you have a good set and will need a bit of heat applied to the back of the knob to allow you to twist and pull them off. I wouldn't allow the heat to get the shaft hot though.