Pentair Pool Heater E01 Error Code

Updated 2026-08-29 · review status: manual-verified Last verified: 2026-08-29

Quick answer

Open Water Temp Sensor Water temperature sensor circuit is open. The control board cannot read the inlet water temperature and has disabled heater operation. Sensor connector disconnected or corroded at the manifold, broken wire in the sensor harness, thermistor element failed open from age or water intrusion. Power-cycle the heater. If E01 persists, inspect the water temp sensor connector on the

Severity: high · DIY difficulty: intermediate

Safety

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What E01 means

Open Water Temp Sensor Water temperature sensor circuit is open. The control board cannot read the inlet water temperature and has disabled heater operation. Sensor connector disconnected or corroded at the manifold, broken wire in the sensor harness, thermistor element failed open from age or water intrusion. Power-cycle the heater. If E01 persists, inspect the water temp sensor connector on the heater manifold. Measure sensor resistance — should read approximately 10kΩ at 77°F. Infinite resistance confirms an open/failed sensor that must be replaced.

Causes, ranked

  1. 1. Water temperature thermistor failed open common pro-only

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  2. 2. Corroded or loose sensor connector at the control board common diy-ok

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    Fix:

  3. 3. Broken/disconnected thermistor wiring between sensor and board occasional diy-ok

    Check:

    Fix:

Parts & supplies for Pentair Pool Heater: filters, control boards, sensors, and common replacement parts.

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Sources

  • PoolDial error-code reference (manual-backed) — verified 2026-08-29
  • Pentair MasterTemp/Max-E-Therm Heater Installation & User's Guide (Section 5 Troubleshooting) — verified 2026-08-29