55.2-59 57 electric wiper question

[QBRacing]

so I have a 57 cab on my 58 Apache and it is running a single power wire with the turn knob control for speed (see attachment).

is the power wire meant to go direct to fused 12v and if so I therefore assume the turntable switch is meant to control the earth contact to engage the wiper ....

or

is the power wire meant to go to a switch and the turntable knob simply controls the speed function.

I only ask as no matter what position my turn knob is in it goes the 1 speed when 12v is applied to the red wire....

cheers

q