Interactive diagnostic wizard for Hayward HeatPro heat pump error codes including LP, HP/HI, PO/OP, Pc/SH, Flo/PS, and sensor faults.
Select the symptom or error code your HeatPro is displaying to get step-by-step troubleshooting guidance.
Click a symptom or error code to see diagnostic steps.
This interactive troubleshooting wizard is designed specifically for the Hayward HeatPro pool heat pump. Whether you are a pool homeowner trying to decode an error code on your heat pump display or a service technician running a structured diagnostic, the wizard adapts to your role and provides the appropriate level of guidance.
Select the "Homeowner" role for safe, practical checks you can perform yourself, or switch to "Technician" mode for detailed diagnostic procedures including refrigerant pressure readings, sensor resistance tests, and component inspections. Each symptom card links to the relevant diagnostic steps from the official Hayward troubleshooting guide.
The table below summarizes the most common Hayward HeatPro error codes and their meanings. Click the troubleshooter above for step-by-step diagnosis of each code.
| Error Code | Description |
|---|---|
| LP | Low Pressure Switch open — refrigerant pressure dropped below 80 PSI, typically from a refrigerant leak |
| HP / HI | High Pressure Switch open — refrigerant pressure exceeded 590 PSI, usually from restricted water flow |
| PO / OP | Open water temperature sensor — sensor circuit is open (infinite resistance) |
| Pc / SH | Shorted water temperature sensor — sensor circuit is shorted (near-zero resistance) |
| Flo / PS | Water Pressure Switch open — insufficient water flow detected through the heat pump |
| dPO / cOP | Open defrost temperature sensor — defrost sensor circuit is open |
| dPc / cSH | Shorted defrost temperature sensor — defrost sensor circuit is shorted |
| FS / deF | Defrost mode active — normal below mid-50°F ambient, abnormal above |
| Blank Display | No low voltage to control — tripped breaker or blown 1A fuse on interface board |
For a complete walkthrough of every error code with photos and wiring diagrams, see the full Hayward HeatPro troubleshooting guide.
LP means the low pressure switch is open because refrigerant pressure dropped below 80 PSI. The switch will automatically reset when pressure rises above 120 PSI. The most common cause is a refrigerant leak in the system. Sustained ambient temperatures below 21 degrees Fahrenheit can also trigger LP, but it will clear automatically when temperatures rise above 40 degrees. A bad LP switch or failed fan motor capacitor can also cause intermittent LP codes.
HP or HI indicates the high pressure switch has opened because refrigerant pressure exceeded 590 PSI. The switch resets automatically at 440 PSI. The most common cause is restricted water flow. Check for an open bypass valve, a dirty filter, or insufficient flow rate. All HeatPro heat pumps require a minimum of 30 GPM water flow, and at higher water temperatures at least 40 GPM may be required. A failed TXV (thermostatic expansion valve) or refrigerant overcharge can also cause this code.
Flo or PS indicates the water pressure switch is open. Although the switch can fail, the majority of Flo/PS errors are water-flow related. Confirm the pool pump is running, the filter is clean, and bypass valves are closed before troubleshooting further. If flow is confirmed, check continuity of the pressure switch with the pump running. If there is no continuity, try adjusting the switch thumbscrew counterclockwise one full turn.
A blank display means there is no low voltage reaching the control board. A tripped breaker is the most common cause. On HeatPro models specifically, a blown 1A fuse on the interface board will also result in a blank display. Check for 240V at the contactor L1 and L2 terminals, then check for 24V AC between the blue and yellow transformer wires. If 24V is present, check the interface board fuse. Common causes of a blown fuse include pinched or shorted low-voltage wires to the pressure switches.
Yes, FS or deF indicates the heat pump is in defrost mode, which is normal when outdoor ambient temperatures are in the mid-50s Fahrenheit or below. The HeatPro runs the fan for 15-minute cycles while the compressor is off to defrost the evaporator coil. If you see FS/deF when temperatures are above the mid-50s, the defrost temperature sensor may be failing and should be checked against the resistance chart in the manual.
Yes. Select the "Homeowner" role and the wizard will show only the checks that are safe and practical for a non-professional to perform. Technician-level steps such as refrigerant pressure measurements and sensor resistance tests are hidden unless you switch to Technician mode. Heat pumps operate on 240 volts and contain R-410A refrigerant, so always follow the safety warnings on screen and consult a qualified pool service professional for any repair you are not comfortable performing.
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