Question: My Magna 3 pump is running with a under voltage error showing a code 75 on a fully lit screen when it is powered off . This is still the case even when I pull the breaker. Why is this happening when no power is turned on?
Answer: I would safely bet that when it was piped, no check valves were installed on the discharge side and the backflow is powering the pump.
Another thing to check is to open up the faceplate and see if the green molex plug module is securely pushed in. Occasionally the electrician used hard instead of the recommended stranded wire and when the faceplate is closed, the hard wire pulls the plug just enough to run and send low voltage fault code. Always try this first.
ECM’s take roughly half the energy to run as opposed to a standard asynchronous motor. When the ghost water is flowing back through the non-powered pump, it is being energized just enough to run.