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Swimming Pool Heat Pump Error Codes

  • 7 min read

There’s nothing worse than eagerly running outside to dive into your pool only to discover your pool heat pump not heating and an error code sitting there to greet you.

While your gut reaction may be to panic or call the manufacturer, retailer, or installer, take a deep breath - we’re going to walk you through some of the most common swimming pool heat pump error codes here in this guide.

We’ll cover the pool heater error codes for AquaCal of course, but you’ll also gain insights on error codes for manufacturers ranging from Pentair to Hayward, Jandy, and more. 

From the cause behind the code to tips on resetting it and getting your heater back up and running, this is the ultimate resource in troubleshooting pool heaters! 

What are the Most Common AquaCal Swimming Pool Heat Pump Error Codes?

There’s no question that AquaCal is among the most reliable manufacturers in the entire pool heating industry. These USA-manufactured pumps are as dependable and long-lasting as it gets. 

Still, it’s not uncommon to deal with an error code here and there. These pumps are equipped with a diagnostic system that displays error codes to help identify specific issues. A lot of the time it’s a quick and easy fix, so you don’t need to stress about this. 

That being said, if you ever feel like you’re in over your head it’s a good idea to get in touch with an expert for professional guidance or repair. In the meantime, here are the most common AquaCal swimming pool heat pump error codes.


Issue: The heat pump detects low or no water flow.

Resolution: Ensure the filter pump is on and running at a sufficient speed. Check for any diversion of water away from the heat pump. Refer to the model’s manual for maximum flow rate recommendations.


Issue: Possible loose or damaged communication cable between the control board and display assembly.

Resolution: Call a qualified technician for inspection and potential replacement of the cable.


Issue: General control system malfunction.

Resolution: Reset the power to the unit to clear the error and restart the system.

dPC | dPO

Issue: The defrost sensor is either shorted or open.

Resolution: The defrost sensor needs replacement by a qualified technician.


Issue: The water temperature sensor is either shorted or open.

Resolution: Replacement of the water sensor by a certified technician is necessary.


Issue: The refrigerant system’s high-pressure switch has triggered.

Resolution: Ensure adequate water flow and check for any obstructions. Calibration of the water pressure switch might be needed.


Issue: Repeated high-pressure faults have occurred.

Resolution: Reset the heat pump and address the underlying high-pressure issues as per the HP error troubleshooting.


Issue: The refrigerant system’s low-pressure switch has triggered.

Resolution: Verify that the filter pump is operational at the correct speed and that no water is being diverted. Check and adjust the water pressure switch calibration if necessary.


Issue: The unit has locked due to multiple low-pressure faults.

Resolution: Reactivate the power to clear the error and conduct troubleshooting based on the LP error guidelines.


Issue: Incoming water temperature has exceeded 110°F.

Resolution: Investigate if another heat source is excessively heating the water. Check the accuracy of the heat pump’s water temperature sensor and replace if necessary.

Pool Heater Error Codes For Other Brands

Pool Heater Error Codes

If you aren’t the proud owner of an AquaCal heat pump, that’s too bad! You should strongly consider upgrading as this pool heat pump is the #1 choice in the USA. 

However, we won’t leave you hanging. Here are some more pool heater error codes for other brands, ranging from Pentair to Gulfstream.


  • LOW FLOW: Indicates insufficient water flow detected, possibly due to a turned valve, clogged line, or pump issues. Ensure the pool pump is on, clean the pump and filter, adjust water valves, or contact the factory for service if unresolved.
  • DEFROSTING: Triggered when ambient air temperature is too low for heater operation. The unit will resume once ambient temperatures increase to appropriate levels.
  • LOW REFRIGERANT PRESSURE: Suggests a possible refrigerant leak. Requires professional service to address the leak.
  • HIGH REFRIGERANT PRESSURE: Indicates water flow restriction or a valve issue restricting flow. Clean pump and filter, adjust water valves, or call the factory for service if ongoing.
  • HP3 Water Lockout: Also signifies water flow restriction similar to the high refrigerant pressure. Follow the same steps as HIGH REFRIGERANT PRESSURE.
  • HIGH WATER TEMPERATURE: Caused by a heater control malfunction or an external heat source. Professional service needed to address control issues.
  • EVAP SENSOR MALFUNCTION: Indicates issues with the defrost sensor, either malfunctioning or disconnected. Requires factory service to correct.
  • WATER SENSOR MALFUNCTION: Points to problems with the water temperature sensor, either malfunctioning or disconnected. Professional service is necessary for repair.


  • HIGH WATER TEMP: Detected when the temperature sensor senses water above 107 degrees. Verify temperature with a thermometer; consult a technician if you find a discrepancy.
  • LOW WATER TEMP: Activates when water temperature drops below 40 degrees. Similar troubleshooting as HIGH WATER TEMP - consult a technician for detailed inspection.
  • LOW WATER FLOW: Occurs when low water flow is detected by the unit’s pressure switch. Ensure adequate water is being pumped and check multiport valve settings. Consider professional help for pressure switch issues.
  • REMOTE POOL/SPA: Indicates simultaneous remote inputs being triggered. Avoid concurrent triggering of inputs.
  • WATER THERM SHORT: Triggered by a shorted water thermistor circuit. Replace the water thermistor.
  • WATER THERM OPEN: Activated when the water thermistor circuit is continuously receiving power. Professional troubleshooting of the water thermistor is recommended.


  • PS | FLo: Indicates low water pressure detected, affecting heat pump operation. Check water levels, ensure adequate water supply to the pump, and clear any clogs.
  • LP | LP3: Signals obstruction in airflow or repeated low-pressure faults leading to a unit shutdown. Clear any blockages around vents, consult a technician if persistent.
  • HP | HI | HP3: Represents either low water flow or high water temperature; HP3 indicates multiple high-pressure faults. Check water flow, verify pool temperature with a thermometer, and troubleshoot with a technician if needed.
  • SH | SF | OP | Pc: Indicates a short or fault in the water temperature sensor. Replace or troubleshoot the sensor with professional help.
  • dPo | dPc: Suggests issues with the temperature probe on the suction side, either disconnected, open, or shorted. Professional inspection and replacement of the probe are recommended


  • Check IGN Control: Indicates potential problems with the ignition control system, such as a faulty ignition module or wiring issues. Professional assistance is usually required to address this.
  • AGS (Automatic Gas Shutdown): Triggered by a fault during the ignition sequence, leading to an automatic shutdown for safety. This could stem from gas delivery problems or ignition issues.
  • Flame Failure: Occurs when the heater detects a failure to ignite a flame, possibly due to issues with the gas supply, a blocked gas valve, or a faulty sensor. This requires inspection by a qualified technician.
  • Service or Call Service: Signals a serious issue within the heater, necessitating professional service. This could involve internal component failures or sensor and circuitry problems.
  • Fault: A general fault code indicating the need to check for other specific codes and consult the owner’s manual for further troubleshooting.


  • E01 or ERR01: Suggests a problem with the flow sensor, possibly due to inadequate water flow, a malfunctioning sensor, or a plumbing blockage.
  • E02 or ERR02: Indicates that the high-temperature limit switch has tripped, likely caused by poor water flow, thermostat issues, or other factors affecting water temperature.
  • E05 or ERR05: Relates to ignition or flame failure, which could arise from complications with the gas supply, blocked gas valve, or issues with the ignition control.
  • E06 or ERR06: Points to a problem with the pressure switch or related pressure issues, such as insufficient gas pressure. Professional evaluation is recommended.
  • E07 or ERR07: Indicates a malfunction with the temperature sensor, often due to sensor or wiring faults.
  • E09 or ERR09: Suggests issues with the combustion air pressure switch, potentially caused by problems with air intake or exhaust.

Still Struggling to Clear Your Heat Pump’s Error Codes?

If you bought your AquaCal HeatWave SuperQuiet Pool Heater or AquaCal TropiCal Heat Pump here at Outdoor Direct and can’t seem to get the pump running properly, don’t hesitate to reach out. We can help you troubleshoot the issue to restore functionality.

On the other hand, if you have a pump from one of the other manufacturers we’ve discussed today and are tired of constantly dealing with swimming pool heat pump error codes, it may be time to consider making an upgrade. 

You can invest in the best pool heat pump here at Outdoor Direct and enjoy far fewer headaches associated with your pump. We source our equipment straight from AquaCal and you can rest assured you’re getting a dependable, efficient, high-performance solution.

Whether you need a small pool heat pump, commercial pool heat pump, above ground pool heat pump, AquaCal chiller, or even pool heater chiller combo, we’ve got the perfect solution for you. 

Shopping with us gets you the lowest pool heat pump costs as well as we don’t charge sales tax and we ship your unit free. You can also use our pool heat pump sizing guide or take our quiz below to ensure you’re getting the optimal pump for your pool’s needs.

Still not sure which heat pump is right for you?

Bringing Our Guide on Swimming Pool Heat Pump Error Codes to a Close

Seeing swimming pool heat pump error codes can be stressful, and the thought of diagnosing the issue yourself can be overwhelming. Hopefully, this guide has left you with a clear understanding of your next steps.

Whether it’s AquaCal, Gulfstream, Pentair, or Hayward, each code provides clues on necessary actions to ensure safety and efficiency of your pump. When in doubt, though, reach out - you don’t want to do more harm than good, after all.

Want to learn more about heating your pool? Our blog has a variety of additional resources like how long to heat pool, how long to run a heat pump per day, pool heat pump life expectancy, pool heat pump vs gas heater, pool heat pump installation, solar vs heat pump pool heater, how warm can a heat pump get a pool, and more.

Otherwise, start troubleshooting your equipment with the insights on pool heater error codes we’ve shared today. Or better yet, upgrade to one of the most sophisticated, high-efficiency pool heat pumps on the market at Outdoor Direct today!