Jandy LXi Troubleshooting Guide: LED Codes, Fault Messages, and Common Problems

The Jandy LXi is a gas-fired pool and spa heater by Zodiac, available in two sizes: the LXi 250 (250,000 BTU/hr) and LXi 400 (399,000 BTU/hr), in both Natural Gas and LP configurations. It uses a premix forced-draft combustion system with hot surface ignition, electronic thermostat control, and an advanced microprocessor controller with LCD display.

This guide is written for working pool service technicians. It covers every LED diagnostic code and fault message the LXi can display, links to detailed troubleshooting articles for each, and provides the practical context you need to diagnose problems in the field. Assume you are standing in front of the heater with the panel open, a multimeter in hand, and the manual nearby.

Quick Reference: LXi Fault Messages and LED Codes

Complete Fault Code Table

Indicator	Description	Severity	Reset Method
LED On Continuously	Ignition Control Fault	Critical	Refer to qualified service personnel
LED Single Flash	Air flow fault (blower pressure switch)	Standard	Clear obstruction, cycle heater
LED Double Flash	Flame exists when NO call for heat	Critical	Refer to qualified service personnel
LED Triple Flash	Ignition lockout (3 failed attempts)	Standard	Turn control off then back to Pool/Spa
NO FLOW	Water pressure switch open (no flow)	Standard	Auto-clears with flow
FAULT-HIGH LIMIT	Water temp exceeds limit switch threshold	Critical	Auto-clears when temp drops; investigate cause
FAULT-FUSELINK/FIELD	Roll-out fusible link (152°C) or vent temp limit (240°C) tripped	Critical	Replace fusible link after investigating cause
FAULT-CHECK IGN CONTROL	Fan/tubing issue, no flame, or low gas pressure	Standard	Diagnose per service guide
FAULT-SHORTED H2O SENSOR	Water temperature sensor shorted	Standard	Check wiring or replace sensor
FAULT-OPEN WATER SENSOR	Water temperature sensor open circuit	Standard	Check wiring or replace sensor
FAULT-PUMP	Pump not running (normal in Maintain Temp mode)	Informational	No service required if in Maintain Temp mode

LXi Model Overview

Understanding which model you are working on matters because temperature rise targets and vent sizing differ:

• LXi 250 — 250,000 BTU/hr, minimum 30 GPM, 6″ vent diameter, temperature rise 8–12°F
• LXi 400 — 399,000 BTU/hr, minimum 30 GPM, 8″ vent diameter, temperature rise 14–21°F

Both models are available in Natural Gas and LP. The LXi uses 120VAC or 240VAC power, and features reversible water connections (left or right side). Maximum water flow is 125 GPM, and maximum working water pressure is 75 PSI.

Key Technical Details

• Ignition type: Hot Surface Ignition (HSI). No standing pilot on any LXi model.
• Combustion: Premix forced-draft with combustion blower and air pressure switch verification.
• Gas pressures: Natural Gas manifold 2.5″ WC (supply 5.0–10.5″ WC). LP manifold 9.0″ WC (supply 11.0–14.0″ WC).
• Burner throat pressure: 1.0″ WC target for all models.
• Limit switches: Two switches — 150°F (65°C, red dot, lower well) and 130°F (55°C, no dot, upper well). Do not interchange.
• Fusible links: Air box 152°C (no marking) and vent box 240°C (red paint). Do not interchange.
• Minimum water temperature: Do not operate below 70°F (21°C).
• Maximum spa temperature: 104°F (40°C).
• Flame current: Should not be less than 1.5 micro-amps measured at the FC pins on the ignition control.
• Automation: Compatible with AquaLink RS control systems via 2-wire connection.
• Electrical: 120VAC or 240VAC. Transformer secondary should read 20–28 VAC.

Ignition Control LED Codes

The ignition controller on the LXi has a dedicated LED that provides diagnostic information independent of the LCD display:

• LED on continuously: Ignition control fault. The ignition control module itself has failed. This requires replacement of the ignition control by qualified service personnel.
• LED single flash: Air flow fault. The blower pressure switch is not closing, meaning insufficient combustion air. Check the blower, pressure tubing, and vent system.
• LED double flash: Flame exists when there is no call for heat. This is a serious safety condition. The gas valve may be leaking through, or the flame sensor circuit may be faulty. Refer to qualified service personnel immediately.
• LED triple flash: Ignition lockout. The heater has attempted ignition three times and failed all three. Turn the control off and back to Pool or Spa mode to get three more attempts.

When To Call a Specialist

• FAULT-HIGH LIMIT or FAULT-FUSELINK/FIELD that trips repeatedly after investigation, indicating a serious flow or heat exchanger problem.
• Gas smell around the heater at any time, especially during ignition attempts.
• LED double flash (flame present with no heat call) — potential gas valve leak-through.
• Soot buildup in the combustion chamber indicating incomplete combustion.
• Any situation requiring gas line work, orifice changes between NG and LP, or gas valve replacement.
• Damaged or cracked heat exchanger headers or visible corrosion.