IXI & JXi Heater Not Heating – Causes & Fixes

If your AstralPool IXI or Zodiac JXi gas pool heater is not heating, the problem is usually caused by low water flow, ignition failure, overheating shutdown, or a fault message such as Check Flow or High Limit.

AstralPool IXI and Zodiac JXi gas pool heaters use text-based fault messages rather than traditional numeric error codes, so identifying the exact fault is the fastest way to diagnose why the heater is not producing heat.

If your heater is not heating, start by checking whether it is displaying a fault message and then work through the related guides below.

Most Common Reasons an IXI or JXi Heater Is Not Heating

• Check Flow fault caused by poor water circulation
• Ignition fault stopping the burner from lighting
• High Limit fault caused by overheating
• Gas supply turned off or gas pressure issue
• Blocked filter or restricted plumbing
• Water sensor fault affecting temperature readings

If your heater has stopped producing heat completely, it is often linked to a Check Flow fault or an ignition issue.

Step-by-Step Checks

• Check whether the heater display is showing a fault message
• Make sure the circulation pump is running properly
• Clean or backwash the pool filter
• Check pump basket and skimmer basket for blockages
• Make sure all valves are fully open
• Confirm the gas supply is turned on
• Restart the heater and observe the startup sequence

If the heater tries to start but then shuts down, it may also relate to an airflow or combustion-related fault.

Related IXI & JXi Fault Guides

• Check Flow Fault – Low water flow through the heater
• Ignition Fault – Heater not starting or lighting
• High Limit Fault – Overheating safety shutdown
• High Flue Temperature Fault – Exhaust heat too high
• Water Sensor Fault – Sensor or wiring problem

Full IXI & JXi Fault Guide

For a complete breakdown of all AstralPool IXI and Zodiac JXi heater faults, see:

IXI & JXi Gas Heater Error Codes Guide →

When to Book a Heater Repair

If your IXI or JXi heater is not heating after basic checks, it likely needs professional diagnosis. Continuing to reset the heater without fixing the underlying issue can cause repeated shutdowns and unnecessary wear.

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.