A liquid application apparatus includes a plurality of control assemblies,each with inputand output ports, a liquid information sensor, and a position controlled valveactivatoroperative to activate a valve to vary a flow opening size. A controllerreceives liquid andposition information and sets each control assembly to dispense the samedesired rate offlow of liquid from the each output port by activating each valve activator tomove thevalve activator to a valve position where the size of the flow openingachieves the desiredrate of flow. The controller is operative to compare a position of the valveactivator in afirst control assembly with the positions of the valve activators in othercontrolassemblies to determine a malfunction. The liquid information sensor istypically a flowsensor or a pressure sensor.
