Hayward Pool Heater Error Codes: What the Display Means

Updated 2026-09-07 · topics: General reference · Sensor faults · Airflow & filters · Power & electronics

Start with the model, not the search result

Hayward uses different displays and diagnostic tables across gas heaters and heat pumps. Find the model and serial label, then identify the family before assigning a meaning. A Universal H-Series gas heater and a HeatPro or Summit heat pump do not share one universal code list.

Take a photo of the complete display before switching anything off. A capital I can look like the number 1 on a small heater display, so a search for "1F" may describe a display that actually reads "IF". If the characters could be IF, 1F, SF, or 5F, do not guess. Compare the photo with the manual for the exact model.

The Hayward hub and Hayward pool-heater code index are useful starting points, but the model manual controls when a code table differs.

Common Universal H-Series gas-heater codes

The Universal H-Series consumer troubleshooting guide identifies these display meanings for its HxxxFD(N/P) family. Confirm that your heater belongs to this family before using the list.

• IF: Ignition Failure. The manufacturer guide describes a limited retry sequence followed by lockout and timed retries. It does not mean that a homeowner should adjust gas pressure or work on the ignition system.
• IO: Ignitor Circuit Open. The code points to the ignitor circuit in this control family. Wiring, resistance tests, ignitor replacement, and control-board diagnosis are service work.
• SF: Temperature Sensor, or thermistor, input failure. This is not a general "system failure" label, and it is not a safe reason to open the heater and probe the sensor circuit.
• LO: Water pressure switch, vent pressure switch, or temperature limit switch fault. A pump or water-flow problem may be involved, but a limit, vent, or pressure-switch diagnosis belongs to qualified service.
• AO: Blower vacuum switch open. This is part of the gas heater's combustion-air and blower safety sequence. Check only for obvious exterior debris around the heater and vent termination; do not open the blower or tubing system.
• PF: Voltage polarity reversed or low voltage detected. Treat this as an electrical warning, not as permission to inspect terminals. A qualified electrician or heater technician should diagnose the supply and grounding path.
• HS: Maximum return-water temperature exceeded or rapid water-temperature rise. Use the exterior flow checks below, then stop if the code returns.

Safe checks you can do from outside

• Confirm the circulation pump is running. Hayward's support guidance puts the filter pump first when a heater will not start. Check the normal pump schedule, that the pump is primed, and that the heater is enabled with a set point above the current water temperature.
• Check the filter and normal valve position. If the filter needs cleaning, follow the filter manufacturer's procedure and relieve system pressure as directed. Do not move a filter valve while the pump is running, and do not change a bypass setting unless the heater and plumbing manual tells you how.
• Look for visible outside blockage. With the heater off, clear loose leaves or objects around the unit and any accessible vent termination. Do not remove vent parts, reach into the cabinet, or disturb combustion-air components.
• Check for obvious exterior damage or water intrusion. Stop using the heater if you see damaged wiring, a wet electrical area, smoke, scorching, or a breaker or GFCI that trips again.
• Use only the reset described for your exact model. If the manual allows a mode change or power reset after the cause has been corrected, perform it once while watching the display. Repeated resets do not repair an ignition, sensor, flow, safety, or electrical fault.

Write down the code, water temperature, pump state, filter pressure if you normally record it, and what happened just before the code appeared. That information is more useful to a technician than a guessed part diagnosis.

How to read IF, 1F, SF, and similar searches

IF versus 1F: The Universal H-Series guide writes the code as IF, with a capital I. A display font can make that character look like 1, but the site cannot safely convert every "1F" search into IF without the model and a clear display photo. Use the Hayward IF / IO reference only when your heater's manual uses that code family.

SF: In the Universal H-Series gas-heater documentation, SF is a temperature-sensor input failure. The Hayward SF reference covers that family. Do not assume that SF has the same meaning on a heat pump, an older heater, or another control board.

5F and other unclear readings: A search phrase such as "5F code" is not enough evidence to assign a Hayward meaning. Photograph the screen, check the model label, and use the exact owner or troubleshooting manual. A two-character display should never be decoded by resemblance alone.

Gas heater and heat pump codes are different

The Hayward/Summit heat-pump troubleshooting guide uses a different set of display families, including LP, HP or HI, PO or OP, Pc or SH, Flo or PS, and FS or deF. Those entries cover refrigeration, water-temperature sensing, water flow, and defrost behavior. They are not alternate explanations for the Universal H-Series gas-heater codes above.

For a heat pump, an LP, HP, HI, or similar pressure-related display can cross into refrigerant or sealed-system diagnosis. A PO, OP, Pc, or SH display may need sensor testing that is not an exterior user check. Follow the exact heat-pump manual and stop before opening the electrical or refrigeration system.

If your equipment is a different Hayward family, start at the Hayward troubleshooting-guide library and choose the guide that matches the model.

When to stop and call qualified service

• The code returns after the permitted exterior checks or one model-approved reset.
• The display involves ignition, flame, venting, a limit, low voltage, polarity, a sensor circuit, or a control-board fault and the problem is not resolved by the documented exterior checks.
• The heater needs its cabinet opened, gas pressure checked, burner or ignitor inspected, combustion tested, wiring measured, a board or sensor replaced, or a refrigerant circuit accessed.
• You smell gas. Do not try to light the appliance or operate electrical switches. Leave the area and follow the gas supplier or emergency instructions in the manual.
• You see smoke, scorching, damaged wiring, standing water in an electrical area, repeated breaker or GFCI trips, or unsafe pool circulation conditions.

Use the code history when you book service

Give the technician the exact model, serial number, display photo, code spelling, date and time, pump state, recent filter or plumbing work, and whether the code returned after the documented reset. Keep the heater's manual available so the technician can use the correct code table.

For comparison with another pool-heater family, use the existing Raypak pool-heater reference rather than applying Hayward meanings to a Raypak display. The brand and control family are part of the diagnosis.