Pull a full chorus of stops on the Great:
Pull a chorus of Pedal stops in balance with the Great:
Find out if the volume of the Great and/or Pedal is controlled by the main expression pedal. While playing a chord on the Great, close and open the expression pedal directly over the center-most pedal notes E and F. Do you hear a volume change? If not, the volume of the Great is not controlled by that pedal.
Now repeat this procedure while playing a Pedal note. If its volume remains unchanged, the same is true of the Pedal.