Interactive diagnostic wizard for Jandy LXi gas heater LED codes including ignition lockout (triple flash), NO FLOW, high limit fault, air flow fault, and sensor failures.
Select the symptom or LED code your LXi is displaying to get step-by-step troubleshooting guidance.
Click a symptom or LED code to see diagnostic steps.
This interactive troubleshooting wizard is designed specifically for the Jandy LXi gas pool and spa heater. Whether you are a pool homeowner trying to decode an LED flash pattern on your heater or a service technician running a structured diagnostic, the wizard adapts to your role and provides the appropriate level of guidance.
Select the "Homeowner" role for safe, practical checks you can perform yourself, or switch to "Technician" mode for detailed diagnostic procedures including gas pressure measurements, component resistance tests, and flame sensor inspection. Each symptom card links to a comprehensive written guide when you need to go deeper.
The table below summarizes the most common Jandy LXi LED codes and their meanings. Click the troubleshooter above for step-by-step diagnosis of each code.
| LED Code / Symptom | Description |
|---|---|
| Triple Flash | Ignition Lockout — heater attempted 3 ignition cycles without detecting flame |
| NO FLOW | Water Pressure Switch fault — insufficient water flow detected before ignition |
| High Limit | High Limit Switch tripped — water temperature near heat exchanger exceeded safe threshold |
| Single Flash | Air Flow Fault — combustion air not detected by the air pressure switch |
| Water Sensor Failure | Temperature sensor circuit open or shorted — sensor disconnected or failed |
| Not Heating | Low heat output — heater runs but pool temperature rises slowly or not at all |
| Knocking / Pounding | Water hammer or TRV issue — unusual noise during heater operation |
For a complete walkthrough of every LXi LED code with photos and wiring diagrams, see the full Jandy LXi troubleshooting guide.
A triple flash on the LXi diagnostic LED indicates Ignition Lockout. The heater attempted three ignition cycles without detecting a flame. Common causes include a closed gas supply valve, insufficient gas pressure, a fouled igniter, or a dirty flame sensor. Start by verifying the gas supply is on and other gas appliances are working. Power cycle the heater by turning the breaker off for 30 seconds, then back on to clear the lockout. If it recurs, a technician should inspect the igniter, flame sensor, and gas valve.
NO FLOW means the LXi's pressure switch did not detect adequate water flow before attempting ignition. The most common causes are a dirty filter, a closed valve in the return line, or a pump that is not running at the required minimum flow rate. Clean the filter, open all valves, and verify the pump is running. If the error persists with adequate flow, a technician should test the pressure switch and inspect the header bypass.
The high limit fault trips when the LXi detects water temperature approaching an unsafe level near the heat exchanger, usually because of low flow. Check that the pump is providing adequate flow, the filter is clean, and no bypass valve is diverting too much water away from the heater. If the switch trips repeatedly even with good flow, a technician should test the high limit switches and inspect the heat exchanger for scale buildup.
Knocking or pounding noises from an LXi heater are typically caused by water hammer related to the TRV (Thermal Regulator Valve) or insufficient flow through the heat exchanger. Start by cleaning the pool filter and pump baskets to improve flow. If the noise persists, a technician should inspect the internal bypass, check the TRV for proper operation, and verify the flow rate is within the heater's specifications.
After an ignition lockout (triple flash), power cycle the heater by turning the breaker off for 30 seconds, then back on. The heater will attempt ignition again on the next call for heat. If the lockout recurs, check the gas supply, clean the igniter and flame sensor, and verify gas pressure is within specification before calling a technician.
The Jandy JXi is the newer model that replaced the LXi. Both use similar LED diagnostic codes and share many of the same troubleshooting procedures. The JXi features an updated control board, improved heat exchanger design, and displays CHECK FLOW instead of the LXi's NO FLOW message. If you have a JXi, use the Jandy JXi Troubleshooter for model-specific guidance.
Yes. Select the "Homeowner" role and the wizard will show only the checks that are safe and practical for a non-professional to perform. Technician-level steps such as gas pressure measurements and component testing are hidden unless you switch to Technician mode. Always follow the safety warnings on screen, and consult a licensed pool service professional for any repair you are not comfortable performing.
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