imported post
Seems likely the pot is to adjust the hysteresis or sensitivity of the unit. It might just be a couple plastic hole covers missing, it doesn't seem likely they'd design the thing with open holes facing forward. First off for trouble shooting would be to see if the control module was getting power, check the clutch and the two brakes switch inputs, the vacuum line that feeds the actuator and the actuator itself. Usually with an applied twelve volts to the vacuum valve and a little vacuum applied with a hand pump you can see if the actuator will work with an applied voltage.