Pool Heater Troubleshooting Guide

Why is my pool heater not working?

A pool heater usually stops working due to issues with water flow, gas supply, ignition systems, sensors, or electrical faults. The most common causes include blocked filters, low water flow, ignition failure, faulty pressure switches, or temperature sensor errors.

• Low water flow or dirty filter
• Gas supply or ignition failure (gas heaters)
• Faulty pressure or flow switch
• Temperature sensor or thermostat issues
• Electrical or control board faults

Pool heaters are complex systems that rely on gas supply, electrical components, water flow, sensors, and safety controls to operate correctly. When one part of that sequence fails, the heater may stop heating, shut down, or display an error code.

This guide covers the most common pool heater problems, what they usually mean, and where to go next if your heater is not working properly. Whether you have a gas pool heater or a pool heat pump, this page will help you identify common faults and find the right troubleshooting advice.

Quick Heater Troubleshooting Links

• Gas Pool Heater Troubleshooting
• Pool Heat Pump Troubleshooting
• Hurlcon Heater Error Codes
• Viron Heater Error Codes
• IXI & JXi Gas Heater Error Codes

Most Common Pool Heater Problems

The most common pool heater problems include no heating, ignition failure, heaters shutting off unexpectedly, and error codes caused by flow issues, sensor faults, or component failures.

Common Pool Heater Problems

These are some of the most common faults seen across pool heaters and spa heaters.

Pool Heater Not Heating

If your pool heater is running but not heating, the most common causes are low water flow, blocked filters, faulty pressure switches, or ignition problems.

Read the full Pool Heater Not Heating guide →

Common causes include:

• Low water flow through the heater
• Dirty filter or blocked plumbing
• Faulty pressure switch
• Incorrect temperature settings
• Ignition or burner issues

Read the full Pool Heater Not Heating guide

Pool Heater Not Igniting

Gas pool heaters rely on a controlled ignition sequence. If the heater fails to ignite, it will often shut down as a safety precaution.

Common causes include:

• Gas supply issues
• Faulty ignition electrode
• Ignition module failure
• Flame sensor faults
• Combustion or airflow problems

Troubleshoot Pool Heater Ignition Failure →

Pool Heater Starts Then Stops

If the heater starts for a short period and then shuts down, this usually points to an overheating problem, sensor issue, or interrupted water flow.

Common causes include:

• Overheating protection activated
• Faulty temperature sensor
• Pressure switch problems
• Restricted water flow
• Control board faults

Diagnose a Pool Heater That Starts Then Stops

Gas Pool Heater Troubleshooting

Gas pool heaters are commonly used for swimming pools and spas because they can heat water quickly and are ideal when fast recovery is required. These heaters rely on several systems working together, including gas supply, ignition, combustion, water flow, and temperature control.

Common gas heater faults include:

• Ignition failure
• Flame loss
• Overheating shutdown
• Pressure switch faults
• Temperature sensor faults

View the Gas Pool Heater Troubleshooting guide

Pool Heat Pump Troubleshooting

Pool heat pumps work differently from gas heaters. Instead of combustion, they use compressors, evaporator coils, fans, and refrigerant systems to transfer heat into the pool water.

Common heat pump faults include:

• Poor airflow
• Fan motor failure
• Sensor faults
• Defrost cycle problems
• Low heating performance in cold weather

View the Pool Heat Pump Troubleshooting guide

Heater Brand Troubleshooting

Different heater brands use different control systems, error codes, and component layouts. Use the brand guides below to find more specific troubleshooting information.

Pool Heater Error Codes

Pool heater error codes help identify faults such as ignition failure, low water flow, overheating, and sensor problems. Start with the general guide below, then use the brand-specific guides if your heater displays a known manufacturer code.

View the full Pool Heater Error Codes guide →

Brand-specific troubleshooting pages can help identify what each code means and what the likely fix may be.

Hurlcon gas heaters use a range of fault codes to identify problems with ignition, sensors, overheating, and water flow.

Models commonly covered include:

• Hurlcon HX heaters
• Hurlcon JX heaters
• Hurlcon MX heaters

View Hurlcon Heater Error Codes

Viron Heater Error Codes

Viron gas heaters and spa heaters may display fault codes relating to ignition, temperature protection, flow issues, and component failures.

View Viron Heater Error Codes

Raypak Heater Troubleshooting

Raypak heaters are widely used in pools and spas and can develop faults related to ignition, flame rectification, sensors, and water flow.

View Raypak Heater Troubleshooting

Pentair MasterTemp Heater Troubleshooting

Pentair MasterTemp heaters can display fault conditions relating to thermal regulation, ignition systems, and pressure-related shutdowns.

View Pentair MasterTemp Heater Troubleshooting

Hayward H-Series Heater Troubleshooting

Hayward H-Series heaters may experience common issues such as ignition failure, low flow faults, sensor problems, and heating interruptions.

View Hayward H-Series Heater Troubleshooting

Common Pool Heater Parts That Fail

Many heater problems are caused by relatively small components that wear out or fail over time. Identifying the failed part can help determine whether the heater can be repaired quickly or whether further diagnosis is required.

Common parts that may fail include:

• Pressure switches
• Ignition electrodes
• Flame sensors
• Temperature sensors
• Gas valves
• Control boards
• Flow switches

Browse Heater Parts

When To Call a Pool Heater Technician

Some heater faults can be traced to simple causes such as blocked filters or incorrect settings, but many faults require professional diagnosis and repair. Gas supply problems, electrical faults, combustion issues, and internal component failures should be assessed by a qualified technician.

If your heater is showing an error code, repeatedly shutting down, not igniting, or not heating as it should, a professional inspection may be the fastest way to get it operating again.

Book a Pool Heater Repair

Preventing Pool Heater Problems

Regular maintenance is one of the best ways to reduce unexpected heater faults and extend the life of your system.

Recommended maintenance includes:

• Cleaning filters regularly
• Maintaining correct water flow
• Checking gas supply and operation
• Keeping water chemistry balanced
• Inspecting the heater for wear or corrosion
• Servicing the heater at regular intervals

Preventative maintenance helps reduce breakdowns, improve efficiency, and avoid unnecessary repair costs.

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