Hayward pool heater error codes describe a condition detected by the controls. They do not necessarily identify a failed component. Match the rating plate and manual before treating a code as a repair instruction.
This guide’s table covers the Universal H-Series gas heaters listed in Hayward manual 51300004201 RevE. It does not serve as a universal table for HeatPro heat pumps, HDF heaters, older controls or other regional versions. Use their own manuals when the identification differs.
Record the model and the display together
Photograph the full rating plate and the code. Include the pool, spa or standby indicator and whether the circulation pump is running. On a segmented display, a letter can resemble a number.
IF is commonly typed as 1F. LO can be transcribed as 10. The bO remote status can also be confused with bd, which belongs to a different diagnostic group in the cited manual.
Don’t silently translate an uncertain display. Keep the photograph with the written code so the technician can confirm it. Record the first message and any later messages in their actual order.
The cited RevE cover lists FD models and specified FD ASME versions. Match the complete identifier rather than using only H250 or H400. Fuel, control revision and installation details still matter within that group.
Hayward pool heater error codes in the cited RevE manual
| Display | What the manual identifies | Appropriate next route |
|---|---|---|
| AC | Blower vacuum switch closed when it should be open | Qualified airflow circuit diagnosis |
| AO | Blower vacuum switch open when closure is required | Exterior obstruction observations, then qualified airflow and vent checks |
| bd | Ignition board data or gas valve state faults | Preserve the code and arrange qualified service |
| bO or bo | Remote thermostat bypass operation | Confirm that remote control is intended |
| CE | Communication between ignition and display boards | Qualified internal control connection diagnosis |
| EE | Error detected in the ignition control board | Qualified control diagnosis |
| HF | Flame signal present when the gas valve should be off | Stop use and arrange urgent qualified gas heater service |
| HS | Excessive sensed inlet temperature or an abnormal rapid temperature rise | Stop repeated trials; check operating observations and arrange diagnosis |
| IF | Ignition retry limit exceeded | Follow the ignition failure route |
| IO | Open igniter circuit detected | Qualified igniter circuit diagnosis |
| LO | Open limit string | Determine pump state, flow observations and safety circuit route |
| PF | Supply polarity, voltage or grounding condition | Qualified electrical diagnosis |
| Sb | Keypad button held or detected closed too long | Check for an obviously held external button; service if unresolved |
| SF | Temperature sensor input disagreement or out of range condition | Compare normal temperature observations, then qualified sensor circuit diagnosis |
The table summarizes the fault families; it does not replace the manual’s full diagnostic sequence. For instance, bd has more than one listed condition. The code alone cannot select a board or gas valve for replacement.
Start with normal states, not a reset
The bO display can be correct when an external thermostat controls heating. It does not indicate a physical water bypass or a blower overheat fault. Use the automation control path guide if heating works locally but not remotely.
LO with the circulation pump off can also be expected in the cited troubleshooting sequence. The important distinction is whether it clears once proper circulation is established. LO persisting during a valid heat request needs further investigation.
A displayed water temperature is not itself a fault code. Compare it with the selected pool or spa setpoint and the active mode. If no fault appears but there is no heat, use the operating state checks.
IF, IO and LO need different questions
IF means the allowed ignition attempts did not produce the required successful operation. It does not mean the igniter circuit is necessarily open. IO is the separate code for that detected circuit condition.
For IF, note the normal startup sounds, whether heating appeared to begin and any recent fuel supply work. The Hayward IF guide explains why gas delivery and flame detection must be distinguished. Do not remove panels to watch the burner.
LO refers to a series of safety devices, often called the limit string. Water flow is an owner check, but it is not the only possible reason that circuit opens. The Hayward LO guide separates a pump off indication from a persistent or temperature related trip.
Never bridge a safety switch to make any of these codes disappear. A cleared display would not establish that the underlying operating condition is safe.
CE is not a WiFi diagnosis
In this manual, CE concerns communication between boards inside the heater. It does not mean the phone lost its wireless connection. Reinstalling an app therefore does not address the condition identified by that code.
An app connection failure and a heater fault can occur together. Check the outdoor controller and the heater’s own display separately. Preserve both observations instead of assuming every communication message has the same cause.
Electrical and control board faults require safe internal testing. A dark screen, for example, does not tell an owner whether the supply, transformer or board is responsible. Do not change internal voltage selectors as a trial fix.
Temperature faults do not automatically mean bad sensors
HS can describe actual high sensed temperature or an abnormally fast rise during firing. Restricted heat removal can be part of the investigation. Repeatedly resetting a temperature fault can recreate the same damaging condition.
SF identifies a sensor input problem in the cited table, including disagreement between redundant readings. The technician still needs to check the sensor circuit before choosing a replacement. Record the displayed reading and an independent pool reading after normal circulation.
If heating stops only after a pump speed or valve change, record that transition. The shutdown timing guide shows how to preserve the sequence. A temperature message without operating context can hide the hydraulic cause.
Reset behavior is code specific
The RevE table describes different restart and lockout conditions. For example, IF lists a 60 minute automatic reset, while LO depends on the limit string closing after the problem is corrected. Do not apply one generic reset delay to every code.
Use the applicable owner procedure only after the identified condition has been addressed. Do not keep cycling the breaker to bypass a waiting period. A fault that immediately returns needs diagnosis, not a faster reset.
Gas odor, soot, steam, banging or burning smells override routine troubleshooting. Leave the area if gas is suspected and contact the appropriate emergency or gas service from safety. A heater with an unresolved safety fault should remain out of use.
Prepare the information that determines the next test
Send the full model, serial number, code photo, pump state and selected water body. Add the requested and displayed temperatures, elapsed time before the fault and recent service changes. State whether the fault occurs at startup, during heating or after the pump stops.
Ask the technician to identify the failed condition and verify normal operation after correcting it. Replacing a part without confirming the cause can leave the same fault waiting for the next heating cycle.
