E18
Rheem
External Safety Interlock Open (Flow Switch, Heater Interlock, etc.)
Pump intermittently displays E18 external interlock or safety input open; pump will not run until cleared.
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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
Open contact on external flow switch, Heater safety loop open, Loose wiring on Rheem interlock terminals, Misconfigured external control input
How to Fix / Troubleshooting
Safety First: Turn OFF power before working on low‑voltage interlock wiring.
- Identify interlock devices: Refer to the Rheem wiring diagram to locate all external safety devices wired to the pump (flow switches, heater contacts, emergency stops).
- Check continuity: With a multimeter, test each interlock device for continuity when it should be closed. Replace any failed switches.
- Inspect wiring: Tighten all low‑voltage terminal screws on the Rheem control and check for broken or loose conductors.
- Bypass for testing only: Temporarily jumper the interlock terminals at the control to confirm the pump runs and E18 clears. Remove the jumper immediately and restore proper safety wiring.
- Correct configuration: Ensure the control is programmed for the correct type of interlock (normally open vs normally closed) per Rheem documentation.
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Repair Difficulty
Medium
3/5
Required Part
Rheem Flow Switch
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