E18
SPRSUN
Water Pump Interlock / Pump Feedback Fault
Display shows E18; unit may not start or may shut down during operation.
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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
External circulation pump not running, Faulty pump relay on PCB, Incorrect wiring of pump interlock terminals, Flow switch not closing despite pump running
How to Fix / Troubleshooting
Safety first: Turn off power to both the SPRSUN heater and the circulation pump before working on wiring.
- Confirm pump operation: Make sure the pool pump is actually running and moving water when the heater is commanded on.
- Check interlock wiring: If the heater controls the pump, verify that the pump is wired to the correct relay terminals on the SPRSUN control board as per the wiring diagram.
- Inspect pump relay: Listen for a click from the relay when the heater calls for heat. If the relay does not energize, it may be faulty.
- Verify flow switch: Even if the pump runs, a stuck-open flow switch can cause E18. Inspect and replace the flow switch if necessary.
- Technician service: If wiring and pump are correct, a technician may need to replace the pump relay or main PCB.
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Repair Difficulty
Hard
4/5
Required Part
Pump Relay on Main PCB
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