Hurlcon Gas Heater F0 Error – Thermostat Fault Causes & Fix

The Hurlcon F0 error indicates a fault in the thermostat temperature control system, usually caused by a faulty temperature sensor lead or a failed thermostat PCB.

This is a common issue across Hurlcon gas heaters and equivalent AstralPool HX and JX models. The heater shuts down as a safety precaution when it cannot read temperature correctly.

Note: These Hurlcon heater error codes and faults also apply to AstralPool HX and JX gas heaters, as they are the same heater models rebranded under AstralPool.

This guide explains what the F0 error means, what causes it, and how to fix it.

What Causes a Hurlcon F0 Error?

• Faulty or damaged thermostat sensor lead
• Corrosion in the brass sensor pocket
• Moisture or water ingress affecting sensor tip
• Loose or damaged wiring connections
• Faulty thermostat PCB (control/display board)
• Poor water chemistry causing long-term corrosion

F0 faults are commonly related to temperature sensor issues or electrical faults within the control system.

Which Heaters Does This Apply To?

This F0 error applies to the following Hurlcon and AstralPool gas heater models:

• WX75, WX120
• HX70, HX120 (also AstralPool HX)
• JX130, JX160 (also AstralPool JX)
• MX125, MX150, MX200, MX250, MX300, MX400, MX500
• Natural Gas and LPG models

What Does the Hurlcon F0 Error Mean?

The F0 error indicates that the heater is not receiving a valid temperature signal from the thermostat system.

When this happens, the heater cannot safely regulate temperature, so it shuts down to prevent overheating or damage.

Initial Checks You Can Perform

Before calling a technician, you can perform these basic checks:

• Turn the heater off at the power point
• Wait 30 seconds and restart the system
• Ensure the circulation pump is running
• Confirm water is flowing through the heater

If the error clears temporarily but returns, this usually indicates a failing sensor lead or control board.

How F0 Differs From F1 and F2 Errors

F0 errors are thermostat control faults, whereas:

• F1 errors are temperature safety shutdowns (sensor-related)
• F2 errors are high-temperature shutdowns (hi-limit sensor)

Understanding this difference helps identify whether the issue is a control fault or a temperature-related shutdown.

When to Call a Technician

If the F0 error persists after a reset, the heater should be inspected by a qualified technician.

Thermostat sensors and control boards require proper testing and safe handling to diagnose correctly.

Related Hurlcon Heater Troubleshooting

• Hurlcon Gas Heater Error Codes Guide
• F1 Temperature Fault
• F2 High Temperature Fault
• Ignition Fault
• Overheating Issues

For broader troubleshooting across all gas heater brands, see our Gas Pool & Spa Heater Troubleshooting Guide .

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