Quick reference guide for all Hayward Universal H-Series heater error codes. Search by code, symptom, or keyword to find causes and fixes.
The Hayward Universal H-Series is one of the most popular pool and spa heater lines in North America, spanning models from the H150FD (150,000 BTU) through the H500FD (500,000 BTU). These heaters use a two-character alphanumeric display on the front control panel to communicate operating status and fault conditions.
When something goes wrong, the display shows a two-character error code that identifies the general category of the problem. Some codes indicate informational conditions (like a blank display meaning no power), while others signal urgent safety faults that require immediate attention. Understanding what each code means can help you communicate more effectively with your service technician and avoid unnecessary downtime.
During normal operation, the H-Series display shows the current water temperature. When a fault is detected, the display alternates between the temperature reading and the error code. Some faults lock out the heater until the condition is resolved and the unit is power-cycled, while others allow the heater to retry automatically.
While some error codes have straightforward fixes a homeowner can attempt, many situations require a licensed pool service technician or gas professional:
IF stands for Ignition Failure. It means the heater attempted to ignite but the flame was not detected. Common causes include a closed gas valve, weak igniter, dirty flame sensor, or air in the gas line. Check that your gas supply is on and that other gas appliances in your home are working. If the problem persists after a few retry attempts, call a technician.
The LO code means the safety string is open, which usually indicates a water flow or pressure problem. The most common cause is that the pump is not running, the filter is dirty, or the bypass valve is sending too much water around the heater. Verify your pump has solid prime, clean or backwash the filter, and make sure adequate flow is passing through the heater.
Yes, HF is a critical safety code meaning flame is detected when the gas valve should be closed. This could indicate a leaking gas valve. Shut off the manual gas supply valve immediately, do not attempt to restart the heater, and contact a licensed service technician right away.
A blank display means no power is reaching the control board. Start by checking your breaker panel to see if the heater's breaker has tripped. Verify the voltage selector on the heater matches your supply (120V or 240V). Check the fuses on the heater's internal fuse board. If everything looks correct, the transformer may have failed and professional service is needed.
For most error codes, you can reset the heater by turning it off at the front panel, waiting 30 seconds, and turning it back on. For safety lockout codes (like HF or repeated HS), you may need to power-cycle the heater at the breaker. If the high limit has tripped, there is a physical reset button inside the heater that must be pressed. Always address the root cause before resetting to prevent equipment damage.
This guide is specific to the Hayward Universal H-Series (H150FD through H500FD). Other Hayward heater lines such as the HeatPro heat pump, the older H-Series (non-universal), or the Summit series may use different error codes and diagnostic procedures. Always refer to your specific model's owner manual for accurate troubleshooting information.
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