HX & JX Gas Heaters – Common Faults & Fixes
If you're experiencing issues with your AstralPool or Hurlcon HX120, HX70, JX130, or JX160 gas spa heater, you're not alone. These popular pool and spa heaters are known for their reliability, but like any gas appliance, they can develop faults over time — including ignition failure, overheating, water leaks, and pressure switch errors. On this page, we outline the most common problems found in HX-series gas heaters and explain what may be causing them. Diagnosis and repair of gas appliances should always be carried out by a licensed and qualified professional to ensure safety and compliance with regulations.
HX & JX Heaters work on a 24V AC system, which means most electrical components other than the igniter will have ~21–24V running to & from them when operating correctly. E.g.: 24V to gas valve when opening, 24V to pressure switch, 24V to high limits, etc.
Related Links
- Spare Parts Listing
- New HX 120 Gas Heaters
- New HX 70 Gas Heaters
- New JX 130 Gas Heaters
- New JX 160 Gas Heaters
Faults & Fixes
1. No Flow Detected
Possible Causes: Usually a faulty pressure switch.
2. Ignition Failure (No Flame Detected)
Symptoms: Heater attempts to ignite but fails; may show an ignition or flame failure error.
Possible Causes:
- Dirty or faulty igniter/flame sensor
- Low gas pressure or no gas supply
- Faulty ignition module (HX Module / JX Module) or thermostat PCB
- Faulty gas valve
Fixes:
- Clean or replace igniter/flame sensor
- Check gas supply and pressure
- Replace ignition module, thermostat PCB, or gas valve if necessary
3. Overheating / High Limit Error
Symptoms: Heater shuts down during use; error for high temperature or high limit.
Possible Causes:
- Restricted water flow (blocked filter, low flow rate)
- Faulty high limit switch:
- Faulty bypass valve
Fixes:
- Clean pump filter and confirm water flow
- Replace faulty sensors or high limit switches
- Ensure bypass valve is intact and working
4. No Power / Control Panel Dead
Symptoms: No lights or display on the control panel.
Possible Causes:
- Tripped circuit breaker
- Blown fuse or faulty transformer
- Loose or corroded wiring
- Faulty transformer
Fixes:
- Check power supply and breaker
- Replace transformer
- Inspect and reconnect any loose wires
5. Water Leaks
Symptoms: Water visible under or inside the unit.
Possible Causes:
- Leaking heat exchanger (HX 120 | HX 70 | JX 130 | JX 160)
- Loose fittings or pipe unions
- Leaking seals (seal kits)
Fixes:
- Tighten or replace o-rings at pipe connections
- Replace seals in manifold
- Replace heat exchanger if leaking internally
6. Sooting / Bad Flame
Symptoms: Yellow flames, soot buildup, noisy burner.
Possible Causes:
- Blocked burners
- Incorrect gas-to-air ratio
Fixes:
- Clean burner assembly & heat exchanger
- Adjust gas pressure (licensed technician only)
7. Blower or Fan Not Working (JX 130 & JX 160 Only)
Symptoms: Fan/blower doesn’t start; air pressure fault.
Possible Causes:
- Faulty blower fan motor
- Pressure switch or hose issue
Fixes:
- Replace blower motor if unresponsive
- Inspect or replace air pressure switch and tubing
General Tips
- Always disconnect power and gas before servicing
- Only licensed professionals should handle gas components
- Use stored fault codes to help with diagnostics
Astralpool & Hurlcon HX & JX Gas Heater Error Codes & Symbols
- F0 - Heater locked off. Can't read temperature. Reset Power. May have faulty temperature sensor.
- F1 - Thermostat reads very high temperature. Allow water to cool. Check filters are clean and there is sufficient water flow. Cycle mains power to reset. May have faulty temperature sensor.
- F2 - Heater has gotten too hot. Check filters are clean and there is sufficient water flow. Wait several minutes for water to cool. Cycle mains power to reset. If error re-occurs, replace Hi-Limit Switches, and brass plugs.
- F3 - Temperature fault. Cycle mains power to reset.
- F8 - Commonly caused by faulty temperature sensor in the heat exchanger.
- L - Heater locked out. Heater has tried to ignite too many times. It will automatically retry after 2 minutes. This allows combustion gases to escape before retrying. If it re-occurs, it may be faulty flame sensor, igniter, ignition module, blown burner, bad heat exchanger, etc.
- Q or Ø - Heater is detecting water pressure, and is ready to ignite when temp is below set-point. If this symbol is not appearing when pump is running, check that filters are clean, valves are in correct positions, or replace a faulty pressure switch.
- * - Igniting. Should hear faint sparking sound.
- ^ - Flame Detected. Heater operating. Symbol looks like an upside-down V.
- Smoke coming from heater. Turn off heater immediately. Turn off gas. Do not use heater.