U.S. Motors variable-speed pool pump displays E04 and shuts down during operation, often when running at higher speeds.

Safety first: Turn off power at the breaker and verify the pump is de-energized before disassembling the wet end.

• Inspect for blockage: Remove the pump lid and basket. Check for debris in the strainer basket, suction port, and impeller eye. If needed, remove the pump housing bolts and access the impeller directly to clear obstructions.
• Check impeller rotation: With the wet end open and power off, spin the impeller by hand. It should turn smoothly with minimal resistance. If it feels gritty or stiff, the motor bearings may be failing.
• Verify correct impeller: Confirm the impeller part number matches the U.S. Motors pump model and HP rating. An oversized impeller can overload the motor.
• Measure current draw: With the pump reassembled and running, use a clamp meter on each line conductor and compare to the motor nameplate FLA. If current is high with clean hydraulics, suspect bearing drag or electrical issues.
• Reset and test: After clearing blockages and verifying components, reset the controller and run at a lower speed first. Gradually increase speed while monitoring current.