Digital AO Smith variable-speed pool pump will not start; control shows “ERR1” shortly after power-up.

Safety First: Turn OFF power at the breaker and verify with a non-contact voltage tester before opening any electrical compartment. Water and electricity are dangerous—if you are not comfortable with electrical work, contact a licensed pool technician or electrician.

• Verify supply voltage: With power ON and using a multimeter (by a qualified person), measure voltage at the pump’s line terminals. Compare to the nameplate rating (typically 230V). If voltage is more than ~10% low, the pump may trigger ERR1.
• Inspect wiring connections: Turn power OFF. Remove the motor terminal cover. Check that L1, L2, and ground connections are tight, clean, and free of corrosion or heat damage. Tighten loose screws and clean light corrosion.
• Check wire gauge and run length: Confirm the supply conductors meet AO Smith’s minimum gauge for the pump’s amperage and distance. Long runs with small wire can cause voltage drop; upgrading to a heavier gauge may be required.
• Inspect breaker and disconnect: Ensure the breaker is the correct amperage and not overheating or tripping. Replace any burnt or loose disconnects or breakers.
• Reset the pump: After corrections, restore power and press the pump’s reset/stop-start button. If ERR1 persists with correct voltage, the control board may be misreading line voltage and require replacement.