Pentair Pentair MasterTemp 400,000 BTU Gas Pool/Spa Heater tS Error Fix: Temperature Sensor Fault

Error code tS on the Pentair Pentair MasterTemp 400,000 BTU Gas Pool/Spa Heater means: Temperature Sensor Fault. The water temperature sensor (thermistor) has an open circuit, short circuit, or is reading out of range. The heater cannot regulate water temperature without a functioning sensor and will not operate. Check the sensor connector for corrosion or loose connections. Measure the thermistor resistance — it should change predictively with water temperature (typically 10K-50K ohms depending on temperature). Replace the thermistor sensor if faulty ($15-30).

The most successful fix is "Test and Replace Water Temperature Sensor Thermistor" (medium difficulty, ~40 minutes). Estimated DIY cost: $15-$30. HomeMD has 2 community-ranked fixes for this error.

This error is rated warning severity. It is generally not urgent and can often be resolved with a simple DIY fix.

Yes — the top-ranked community fix ("Test and Replace Water Temperature Sensor Thermistor") is rated medium difficulty and takes about 40 minutes. Tools needed: Multimeter, T20 Torx screwdriver, Needle-nose pliers.

DIY cost: $15-$30. Professional repair typically costs $120-$180. Many homeowners save money by trying the top-ranked community fix first.

The Pentair Pentair MasterTemp 400,000 BTU Gas Pool/Spa Heater has 8 other known error codes, including: AFS (Air Flow Switch Fault), AGS (Auto Gas Shutoff), bd (Board Error), BURNER DEBRIS (Burner Tray Obstruction), BYPASS VALVE (Bypass Valve Adjustment Needed), and 3 more.