Harris variable-speed pool pump displays E03 and will not run or stops intermittently

Safety first: Turn off power at the breaker before opening any electrical covers.

• Measure line voltage: With a multimeter and the breaker ON, measure voltage at the pump input terminals while the pump attempts to start. Compare to the Harris pump rating (e.g., 230V ±10%). If voltage drops significantly under load, you have a supply issue.
• Inspect wiring connections: Turn power OFF. Remove the electrical cover on the Harris control module and check that all line and ground connections are tight and corrosion-free. Tighten any loose lugs.
• Check wire gauge and run length: Verify that the supply cable size matches Harris installation instructions for the distance from the panel. Long runs with small gauge wire can cause excessive voltage drop; upgrading to a larger gauge may be required.
• Isolate the circuit: Ensure the pump is on a dedicated breaker and not sharing with other heavy loads (heaters, large appliances). If it is shared, move the pump to its own circuit.

If E03 continues with proper voltage at the terminals, the internal drive electronics may be faulty and the control module should be replaced.