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Pool heater not working

Swimming Pool Heater Not Working? Here is how to check:

All heating systems, after a few years of operation, can have their share of problems. Because we have been in the heat pump business for so long, we have had the opportunity to help a lot of our customers when they notice their unit is not working properly. Here are some basic steps to check and see if its operating properly before calling a heat pump professional.

    1. Air temperature. As we all know, air-source heat pumps transfer heat from the air to your swimming pool. Therefore, they depend on the air temperature. A heat pump operates more efficiently in warmer air because more heat is present in higher temperatures. Similarly, a heat pump operates less efficiently in cooler air and will need to run for a longer period of time in order to heat your swimming pool.
    2. Temperature difference. What is the temperature difference between the air entering your heat pump and the air exiting your heat pump? It should measure between 9° and 12°F (5° and 7°C). If it does, then your heat pump is operating normally, and your heating failure is most likely due to inadequate run time of the heat pump. Remember, your heat pump’s run time depends on your filtration pump’s operation.
    3. Evaporator coil obstructions. Without sufficient air inflow and outflow, your heat pump will heat less efficiently. An inefficient heat pump will not only heat your swimming pool more slowly, but will also increase your electric bill. Remove all leaves, pine needles, twigs, and other objects from the top and sides of your heat pump.
    4. Flow, Flow, Flow! Constant, sufficient water flow is needed by your heat pump to transfer heat from the refrigerant to your swimming pool. Insufficient water flow will not only lengthen your heating time, but will also cause damage to your heat pump’s internal components. To check your water flow, make sure the valves to your heat pump are completely open and that your filter is clean.

If you’ve already checked all of these items, then you probably need to call for service. AquaCal® is here to help!

This Post Has 36 Comments

  1. My aquacal keeps cutting off with high pressure fault message. I have adjusted pressure and made sure unit is clean.

    1. Hi JD,

      HP/HP5 errors are normally caused by insufficient water flow through the heat pump. Make sure your filter and baskets are clean, make sure there are no valves in the wrong position, and make sure the pool level is half way up the pool skimmer. If you continue to have issues, please call us at 727-823-5642.

      AquaCal Tech Support

  2. OTA high water temp is displayed and my heater isn’t working? Haven’t found how to reset. Water temp is definitely not hot?

    1. Hi, this is most likely the water temp sensor. Please call us at 727-823-5642. Thank-you, Barry.

  3. Have a error code of P0 on my pool heat pump. Anything I can do to fix it? Am on an island with few services.

    1. Hi Brian,
      PO is an Open Water Temp Sensor. The sensor will need to be replaced.
      AquaCal Tech Support

  4. Even though my pool heating light is on it is not heating the pool water. Are there actions i can take to make sure the heater is working. IS there something I can do to address the problem.

    1. Hi Steve,
      When the heating light comes on, you should notice much colder air blowing from the fan. These units also condensate a lot when working properly. It’s normal to see water under the unit while heating. If you do not notice the colder air or condensation, it’s possible the compressor is not coming on. Please call us at 727-823-5642 if you would like to discuss over the phone.

      AquaCal Tech Support

  5. My heat pump shuts off at 94F even though the spa is set to 100F. It was fine a week ago.
    Outside temp is 65F

    1. If the heat pump is shutting off with no error codes before the desired temperature is reached a service call may be needed. Make sure the pool circulation pump isn’t turning off, the filtration is clean and no valves are interfering with the flow of water through the heat pump. Also check to verify there is not an interruption of power to the heat pump.

  6. Good day, I have an Aqua cal heater that the digital display comes on , but displays only the light, nothing else. Swiping to unlock does nothing. Any advise is greatly appreciated.


    1. Good Morning Doug,
      Hope you are doing well. The only suggestion I can give, before having you call in for service, is to turn the breaker to the heat pump off for 5 minutes. This will reboot the system & may bring the display back. If this does not work, call us at 727-823-5642 to get service set up.
      Robert Brown
      AquaCal Tech Support

  7. I just had my temperature sensor on my weather King pool heater changed and the water in the pool is still hotter that what’s being displayed on the control panel.
    Are there any other issues that should be looked for?

    1. Good Evening Julian,
      Hope you are doing well. As we do not manufacture the WeatherKing unit, I cannot provide precise instructions. However, you most likely need to calibrate the control board to the new sensor. IF the control board was calibrated to compensate for the bad sensor, then the board will show a different temp than what the new sensor is actually reading.
      I would check your manual to see if it has the instructions.
      Robert Brown
      AquaCal Tech Support

  8. The unit is displaying a higher temperature than the actual water temperature and therefore shutting of the heater. What could cause this?

    1. Good Morning Lily,
      Hope you are doing well. This is most likely an issue with the water temp sensor.
      I would call Customer Support at 727-823-5642 with your model & serial number to get this in the right direction.
      Robert Brown
      AquaCal Tech Support

  9. Hi. We have a had a new heat aquacal heat pump since February. Had it running last night working fine then a code popped up I turned pool pump off figured I would handle it this am well went out there and now there is no power to unit I have checked all breakers there all reset or on but still no power to unit ??????

  10. Help…unit starts, red light indicating heat is in progress, fan is spinning everything seems to be working but temperature of water not getting warm. No codes displaying problems or error. Thank you!

  11. The unit starts up, but the red heating light doesn’t come on and after a few minutes the Code PH5 appears. I have cleaned the filter, checked the valves. Had this problem a couple of years ago and cleaning the filter did the trick but not this time. Any thoughts. Don

    1. Good Afternoon Don,
      Hope you are doing well. In most cases the HP5 message is water flow related.
      However, in other cases this is a problem with the flow of refrigerant instead. If there is a refrigerant blockage, the compressor may run for 5-10 seconds & then shut the machine down on HP eventually going to HP5 after 5 attempts to run within 1 hour. I would contact us at 727-823-5642 to request a service a call.
      Robert Brown
      AquaCal Tech Support

  12. hi my heater starts perfect then as usual the red indicator of heating turns on red and sound a click in the unit but no hot water its getting out of the heater what could be happening

    1. Good Afternoon Marcos,
      Hope you are doing well. This will most likely be an issue with an internal component not starting your compressor.
      It is best to contact at our factory to have us check for a local service agent.
      Please call Customer Support at 727-823-5642
      Robert Brown
      AquaCal/AutoPilot Tech Support

  13. The outside temp is 86. The water temp reads 82. The pool light and water temp lights are green. The touch screen is frozen. Nothing happens when you index any button. Please advise.

  14. Looking at replacing a dead aquacomfort pool heatpump with an Aquacal. My question is what would I do for service here in southern NJ(zip 08234)? There are no service firms listed within 100 miles. Would an Air conditioning firm be able to repair and order parts from you? Any other idea?

  15. The heat pump tries to start when the pool pump is not on. It makes a loud bumping sound when it tries to start. It does this every 3 or 4 minutes until I set it on OFF. This problem just started. Any suggestions? Thanks.

    1. Hi Karol,

      Our heat pumps recognize water flow with a water pressure switch. When your circulation pump is turned off you should see “FLO” on the display. The heat pump can continue to run after the circulation pump is off when the heat pump is positioned lower than the pool water surface. This difference in height between the heat pump and pool surface can cause enough hydro-static pressure to activate the pressure switch and the heat pump will try to run. There could also be an issue with the pressure switch. Please call us at 727-823-5642 if you have any questions.

  16. I just purchased a brand new heat pump yesterday , it turned on once but after I shut pool pump off
    to clean filter & started it again it will not turn on . I am not getting any error codes , it is displaying water temp ( 70 degrees ) & I have it set at 87 degrees . This is a new client & i need this resolved immediately

  17. the heat pump is showing the actual pool temperature at 85 but the pool thermometer shows 92. is there a way to calibrate the thermometer on the pump?

  18. if the setting is on pool, heat but the heating indicator light is red when the other lights are green, does this mean that the heat isn't working?

    1. Hello Karen-

      Thank you for your question. When the compressor activated, the heading light will show red, red as in hot or heat… heating…. get it? When the compressor is off the light will also be off, in other words, The heating light only comes on red when it's actually heating otherwise the light goes off.

      Please feel free to contact us should you have any further questions.

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