It is not likely to be the sensor, what you describe would be related to the PTC shutting down the controller because of excess power demand from the pump. This part of the controller is a circuit breaker that shuts down the pump if the watt draw is excessive. You can verify this if the pumps slows to a stop as it is a thermal device that slowly seperates contact as it gets hot. The culprit could be the pump, the connection or the wiring. You have a brand new pump but new pumps have a double seal that raised the resistance and when brand new the resistance can be high. I would double check that the euro connector is free of any corrosion and if you know the wires have been wet at any point I would cut back the wires and verify that the copper is not oxidized. Worst case we can upgrade the PTC to increase the wattage capacity, we indeed now use a bigger PTC as the new power supply has a higher peak capacity.
