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Jandy · JXi 400,000 BTU Pool and Spa Heater with Digital Temperature Control

Jandy JXi 400,000 BTU Pool and Spa Heater with Digital Temperature Control TO Error Fix: Thermostat Open — Temperature Sensor Disconnected

The water temperature sensor (thermistor) circuit is open — the sensor is physically disconnected, the wire is broken, or the sensor itself has failed; the heater cannot regulate water temperature without a functioning sensor and will not fire; check the sensor connector at the control board for a secure connection; inspect the sensor wire for physical damage, rodent chew marks, or cuts from landscaping; test thermistor resistance with a multimeter (should read approximately 10K ohms at 77°F/25°C); replace the sensor if open circuit

Medium severity2 fixes available✨ Free fix available

Quick Answer

Error TO on the Jandy JXi 400,000 BTU Pool and Spa Heater with Digital Temperature Control means: Thermostat Open — Temperature 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.

When to Call a Professional

While many pool heater repairs can be done safely at home, consider hiring a qualified technician if:

The repair involves electrical wiring, gas lines, or refrigerant
You've tried the top-ranked fix and the error persists
You smell gas, see sparking, or notice water leaking
The repair requires specialized tools you don't have
Your appliance is still under manufacturer warranty

Average professional repair cost for this issue: $150-$200.

Other Jandy Models with Error TO

JXi 260 260,000 BTU Pool Heater with High Efficiency and Digital Temperature Control

pool_heater · 2 fixes

LXi 400,000 BTU Low NOx Pool and Spa Heater

pool_heater · 2 fixes

Other Jandy JXi 400,000 BTU Pool and Spa Heater with Digital Temperature Control Error Codes

AFS

Air Flow Switch Fault

Air/Gas Switch Fault

Communication Error

Combustion Fan Fault

Flue Exhaust Fault

Flow Fault — Insufficient Water Flow

2 fixes

Flame Sense Fault

2 fixes

Gas Fault

2 fixes

People Also Ask About Jandy JXi 400,000 BTU Pool and Spa Heater with Digital Temperature Control Error TO

What does error code TO mean on a Jandy JXi 400,000 BTU Pool and Spa Heater with Digital Temperature Control?

Error code TO on the Jandy JXi 400,000 BTU Pool and Spa Heater with Digital Temperature Control means: Thermostat Open — Temperature Sensor Disconnected. The water temperature sensor (thermistor) circuit is open — the sensor is physically disconnected, the wire is broken, or the sensor itself has failed; the heater cannot regulate water temperature without a functioning sensor and will not fire; check the sensor connector at the control board for a secure connection; inspect the sensor wire for physical damage, rodent chew marks, or cuts from landscaping; test thermistor resistance with a multimeter (should read approximately 10K ohms at 77°F/25°C); replace the sensor if open circuit

How do I fix error code TO on my Jandy JXi 400,000 BTU Pool and Spa Heater with Digital Temperature Control?

The most successful fix is "Test and Replace Water Temperature Sensor (Thermistor)" (medium difficulty, ~30 minutes). Estimated DIY cost: $15-$25. HomeMD has 2 community-ranked fixes for this error.

Is error code TO on a Jandy JXi 400,000 BTU Pool and Spa Heater with Digital Temperature Control serious?

This error is rated medium severity. It should be addressed soon, but your appliance may still function in a limited capacity.

Can I fix Jandy JXi 400,000 BTU Pool and Spa Heater with Digital Temperature Control error TO myself?

Yes — the top-ranked community fix ("Test and Replace Water Temperature Sensor (Thermistor)") is rated medium difficulty and takes about 30 minutes. Tools needed: T20 Torx screwdriver, Digital multimeter.

How much does it cost to repair Jandy JXi 400,000 BTU Pool and Spa Heater with Digital Temperature Control error TO?

DIY cost: $15-$25. Professional repair typically costs $150-$200. Many homeowners save money by trying the top-ranked community fix first.

What other error codes does the Jandy JXi 400,000 BTU Pool and Spa Heater with Digital Temperature Control have?

The Jandy JXi 400,000 BTU Pool and Spa Heater with Digital Temperature Control has 8 other known error codes, including: AFS (Air Flow Switch Fault), AGS (Air/Gas Switch Fault), CE (Communication Error), CF (Combustion Fan Fault), FE (Flue Exhaust Fault), and 3 more.

Which other Jandy models have the TO error?

Error code TO also appears on 2 other Jandy models: JXi 260 260,000 BTU Pool Heater with High Efficiency and Digital Temperature Control, LXi 400,000 BTU Low NOx Pool and Spa Heater. The fix may vary by model, so check each model's specific page for tailored repair steps.

What other error codes does the Jandy JXi 400,000 BTU Pool and Spa Heater with Digital Temperature Control have?

The Jandy JXi 400,000 BTU Pool and Spa Heater with Digital Temperature Control has 8 other known error codes:

AFS — Air Flow Switch Fault (2 fixes)
AGS — Air/Gas Switch Fault (2 fixes)
CE — Communication Error (2 fixes)
CF — Combustion Fan Fault (2 fixes)
FE — Flue Exhaust Fault (2 fixes)
FLO — Flow Fault — Insufficient Water Flow (2 fixes)
FS — Flame Sense Fault (2 fixes)
GF — Gas Fault (2 fixes)

Which other Jandy models have the TO error?

Error code TO also appears on 2 other Jandy models:

JXi 260 260,000 BTU Pool Heater with High Efficiency and Digital Temperature Control (pool heater) · 2 fixes
LXi 400,000 BTU Low NOx Pool and Spa Heater (pool heater) · 2 fixes

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