Hayward Pool Heater SF Error Code

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

Quick answer

Temperature Sensor Failure Temperature sensor (thermistor) input failure. Temperature reading wildly inaccurate or missing. Failed thermistor, damaged sensor wiring or corroded connections, water intrusion in sensor connector. Check sensor connector for corrosion or water damage. Measure thermistor resistance (should read approximately 10kΩ at 77°F). Replace sensor if readings are open or shorted.

Severity: high · DIY difficulty: intermediate

Safety

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What SF means

Temperature Sensor Failure Temperature sensor (thermistor) input failure. Temperature reading wildly inaccurate or missing. Failed thermistor, damaged sensor wiring or corroded connections, water intrusion in sensor connector. Check sensor connector for corrosion or water damage. Measure thermistor resistance (should read approximately 10kΩ at 77°F). Replace sensor if readings are open or shorted.

Causes, ranked

  1. 1. Thermistor error: >5°F difference between the two thermistors, or both sensors out of bounds (<10°F or >180°F) common pro-only

    Check:

    Fix:

  2. 2. Faulty sensor wiring or connector occasional diy-ok

    Check:

    Fix:

Parts & supplies for Hayward 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
  • Hayward H-Series H150FD-H500FD Service & Installation Manual (Figure 27: Error codes) — verified 2026-08-29
  • PoolDial error-code reference (manual-backed) — verified 2026-08-29