IXI & JXi Heater High Flue Temperature Fault – Causes & Fixes

A High Flue Temperature fault on AstralPool IXI and Zodiac JXi gas pool heaters means the exhaust temperature is too high and the heater has shut down for safety.

This fault is usually related to poor ventilation, flue restriction, combustion issues, or excessive heat build-up inside the heater.

Combustion issues may also present as the heater failing to ignite or shutting down shortly after startup.

Common Causes of a High Flue Temperature Fault

• Blocked heat exchanger
• Poor ventilation around the heater
• Blocked or restricted flue
• Internal combustion problem
• Flue temperature sensor issue
• Debris, soot, insects or obstruction inside the heater

If the heater is struggling to ignite or run cleanly, this fault can overlap with an ignition fault or other combustion-related issue.

How to Fix a High Flue Temperature Fault

• Check ventilation around the heater
• Inspect the flue for blockages
• Look for soot, debris or insect activity
• Make sure the heater installation area has proper clearance
• Arrange servicing if the fault returns

If the heater also starts and then shuts down repeatedly, review the heater keeps turning off guide as well.

Common Heater Problems

• Heater Not Heating
• Heater Not Igniting
• Heater Keeps Turning Off

Related IXI & JXi Troubleshooting

• IXI & JXi Gas Heater Error Codes Guide
• Ignition Fault
• High Limit Fault

When to Book a Heater Repair

High flue temperature faults usually require professional inspection, especially if the heater continues to shut down or shows repeated fault messages.

Book a Heater Service or Repair →

This article is for general information only. HeaterFix recommends all gas heater servicing, repairs and replacements be carried out by a qualified licensed gas fitter.