E16
A.O. Smith Recirculation Pump Fault (Models with Built-In Pump)

A.O. Smith water heater shows E16; unit may not heat or may cycle rapidly

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Safety Warning

This repair may involve working with high voltage components or water connections. Always unplug the appliance before removing any panels.

If you are not confident in your ability to perform this repair safely, we strongly recommend contacting a professional technician.

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Possible Causes

Failed internal recirculation pump, Air-locked recirculation line, Blocked check valve in recirc loop, Pump wiring or control failure

How to Fix / Troubleshooting

Safety: Disconnect power and close isolation valves before servicing the pump.

  • 1. Listen and feel: When the recirculation function should be running, place a hand on the pump housing. You should feel vibration and slight warmth. Silence indicates a non-running pump.
  • 2. Bleed air: If the recirc loop was recently installed or drained, bleed air from high points or dedicated purge valves to restore flow.
  • 3. Check valves and filters: Inspect any recirc check valves and strainers for blockage. Clean or replace as needed.
  • 4. Electrical connections: Verify the pump wiring harness is fully connected to the control board and pump terminals.
  • 5. Replace pump: If the pump receives power but does not run, replace the recirculation pump with an OEM A.O. Smith assembly.
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Repair Difficulty

Hard 4/5

Required Part

Recirculation Pump
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