TO
Jandy · LXi 400,000 BTU Low NOx Pool and Spa Heater
The water temperature sensor (thermistor) circuit is open — sensor disconnected, wire broken, or sensor failed; heater cannot regulate temperature; check the sensor connector at the control board, inspect wire for damage, test thermistor resistance (approximately 10K ohms at 77°F); replace sensor if defective
Error TO on the Jandy LXi 400,000 BTU Low NOx Pool and Spa Heater means: Thermostat Open — Sensor Disconnected. The top-ranked community fix is “Test and Replace Water Temperature Sensor (Thermistor)” (medium difficulty, ~30 min, DIY cost: $15-$25). 2 community-ranked fixes available below.
Published February 2026 · 2 fixes · pool heater
Content is based on manufacturer service documentation, community repair experience, and OEM technical bulletins. Always verify with your owner's manual.Learn about our editorial standards.
While many pool heater repairs can be done safely at home, consider hiring a qualified technician if:
Average professional repair cost for this issue: $150-$200.
The Jandy LXi 400,000 BTU Low NOx Pool and Spa Heater has 8 other known error codes:
Error code TO also appears on 2 other Jandy models:
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