E12
Pentair
Low Voltage / Power Supply Fault
Heater displays E12 and shuts down or will not start.
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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
Incorrect line voltage, Loose power connections, Undersized wiring causing voltage drop, Failing transformer or control board power supply
How to Fix / Troubleshooting
Safety: Turn off power at the breaker before opening the electrical compartment.
- Verify supply voltage: Confirm that the heater is wired for the correct voltage (120V or 240V) and that the supply matches the rating on the nameplate.
- Inspect wiring connections: Tighten all line and neutral/ground connections at the heater terminal block. Look for signs of overheating or discoloration.
- Check breaker and wire size: Ensure the circuit breaker and wire gauge meet Pentair’s installation requirements to avoid voltage drop under load.
- Transformer/control check: If line voltage is correct but low-voltage power to the control board is unstable, the internal transformer or board power supply may be failing and should be replaced by a technician.
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Repair Difficulty
Hard
4/5
Required Part
Control Board Power Supply / Transformer
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