Gas Pool & Spa Heater Troubleshooting – Error Codes & Fixes

Why is my gas pool or spa heater not working?

A gas pool or spa heater usually stops working due to ignition failure, gas supply issues, low water flow, overheating, or sensor faults. Most heaters will display an error code or shut down as a safety precaution when a fault is detected.

• Ignition failure or no flame detected
• Gas supply or pressure issues
• Low water flow or blocked filter
• Overheating or temperature safety shutdown
• Faulty sensors or control board issues

If your heater is displaying an error code or not operating correctly, use the guides below to diagnose the problem and find the correct solution.

What Do the Symbols on a Gas Pool Heater Mean?

If your heater shows symbols such as 0, *, ^, or L during startup, this is part of the normal ignition sequence. These symbols indicate which stage of ignition the heater is currently in and can help identify where the process stops.

View the full ignition sequence guide →

Common Gas Pool & Spa Heater Problems

Most gas heater faults fall into a small number of common problem categories related to ignition, water flow, overheating, or system safety shutdown.

• Gas heater not igniting or starting
• Heater starts then stops or short cycles
• Heater running but not heating
• Error codes appearing on the display
• Poor heating performance or slow heating

Common Gas Heater Fault Causes

Many heater problems are caused by specific component or system failures. Identifying the root cause can help diagnose issues faster and avoid unnecessary repairs.

• Water flow problems
• Pressure switch faults
• Temperature sensor faults
• Ignition system failure
• Gas supply or pressure issues
• Control board faults

Viron Gas Pool & Spa Heater Error Codes & Faults

AstralPool Viron gas heaters use digital error codes to identify specific faults including ignition failure, overheating, airflow issues, and sensor problems.

• Viron F0 Error – Control or communication fault
• Viron F1 Error – Flow or low-temperature safety fault
• Viron F2 Error – High-temperature or overheating fault
• Viron F6 Error – Airflow, fan, or pressure switch fault
• Viron F7 Error – Temperature sensor or control fault
• Viron Heater Ignition Fault / Won’t Start
• Viron Heater Overheating or Short Cycling

Hurlcon Gas Pool & Spa Heater Error Codes & Faults

View the complete Hurlcon gas heater error code guide →

Hurlcon gas heaters (HX, WX, JX and MX series, now continued under AstralPool HX and JX models) use multiple safety systems and error codes to protect the heater during abnormal operation.

• Hurlcon F0 Error – Thermostat sensor or PCB fault
• Hurlcon F1 Error – Temperature safety shutdown (45°C limit)
• Hurlcon F2 Error – High-temperature shutdown (52°C limit)
• Hurlcon MX F4 Error – Flame rollout safety shutdown
• Hurlcon Heater Ignition Fault / Won’t Start
• Hurlcon Heater Overheating or Short Cycling

When to Call a Gas Pool Heater Technician

If your gas pool heater is not igniting, repeatedly shutting down, or displaying persistent error codes, professional diagnosis is recommended. Gas supply issues, electrical faults, and internal component failures require licensed repair.

Book a Gas Pool Heater Service →

Need Help Diagnosing a Gas Pool Heater Fault?

If you're unsure what the problem is, start with the main troubleshooting guide:

Pool Heater Troubleshooting Guide →

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