System Stalled - Stroke Sensor Systems (pre-2004)

System Stalled –Stroke Sensor Systems

Older (before 2004) systems used a stroke sensor on the Clark Pump to send a signal that the Clark Pump is cycling. If the MPC controls do not receive a signal from the rotoflo that water is flowing through it properly, or a stroke sensor signal is not being received, the MPC controls will try to start three times, displaying: RE-STARTING, and then alarm SYSTEM STALLED.


On stroke sensor systems, if the Clark pump is shifting, but the MPC alarms, confirm that the green light on the stroke sensor is going on and off with each shift. If the light is blinking and you still get System Stalled, or the pump is cycling but the light is not blinking, perform the Stroke Sensor Test.


If the light is going on and off with each cycle of the Clark pump but you are getting a SYSTEM STALLED alarm, then the signal that the Clark pump is stroking is not getting through to the controller. Check the voltage from the green wire to the black wire in the sensor cable connector. The voltage should cycle between 4.9 volts and 0 volts with each stroke of the Clark pump. If it stays at 4.9 volts, either the stroke sensor is bad or the green signal wire is broken or has a bad connection. Carefully check the wiring.


If the voltage stays at zero while the green light is cycling on and off either the stroke sensor is bad, the Printed Circuit Board is not providing power to the signal terminal, or there is a short in the cabling between Signal and ground. First remove the green signal wire from the connector and check for voltage. If the voltage comes up to 4.9V the sensor is bad or there is a short in the wiring.


If the voltage at the connector stays at zero with the signal wire disconnected, it is a PCB problem. Try moving the wires to the other set of stroke sensor terminals in the connector. If that doesn’t work, replacing the MPC circuit board is indicated.