E12
Rheem
External Control / Thermostat Input Fault
Heater shows E12 and will not respond to thermostat commands
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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 or shorted remote thermostat wiring, Incorrect wiring to pool automation system, Faulty remote temperature sensor
How to Fix / Troubleshooting
Safety First: Turn off power before working on low-voltage wiring.
- Check operating mode: Confirm the heater is set to the correct mode (standalone vs. remote) per the front panel settings.
- Inspect remote wiring: Trace the two-wire or multi-wire cable from the heater to the external controller or thermostat. Look for cuts, splices, or corrosion at terminals.
- Test for shorts: Disconnect the remote wires at the heater and measure resistance between the terminals. An unexpected short or open indicates wiring or remote device issues.
- Bypass remote (for test): Temporarily configure the heater to local control only. If the heater operates normally, the problem is in the external control circuit.
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Repair Difficulty
Medium
3/5
Required Part
Remote Thermostat Wiring
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