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Troubleshooting: My Swimming Pool Heat Pump Will Not Start

Consumers often come to us at AquaCal for help with their swimming pool heat pumps because we have manufactured, distributed, and serviced heat pumps for over 30 years. Sometimes consumers come to us with a simple problem: “my heat pump won’t run.” In order to address this problem and to help others, we discuss a few tests you can perform on your heat pump before you call your heat pump professional.

  1. Check your power source. Heat pump owners often forget to perform this simple check and jump right to more tedious ones. Make sure your breaker has not tripped and that the disconnect switch of your heat pump (located adjacent to your unit, typically on a wall or a post) is turned on.
  2. Ensure that your heat pump is getting sufficient water flow. Just as a dirty filter and basket can cause your heat pump to run less efficiently (see our article “Why Isn’t My Swimming Pool Heat Pump Heating?“), they can also cause your heat pump to stop altogether. Make sure the valves to your heat pump are completely open and your filter and pump basket are clean. Some heat pump installations require a plumbing by-pass in the piping system so as to comply with the heat pump’s maximum flow recommendations. This by-pass allows some of the total flow of water to be diverted from flowing through the heat pump and return directly to the pool. This by-pass valve, if present, should not be adjusted after the installer has properly set it.
  3. Check your desired water temperature and your actual water temperature. Many heat pumps cannot cool a swimming pool, they can only heat it. Therefore, your heat pump may not operate if your swimming pool temperature is higher than the temperature set on your heat pump’s display. Set your desired water temperature above your actual water temperature and check back later to see if your heat pump is operating.
  4. Check the air temperature. An air-source heat pump can form ice on its evaporator coil if it operates in low air temperatures. This ice can block air inflow and damage the air-source heat pump’s internal components. Some air-source heat pumps are therefore designed to automatically shut off or activate a defrosting system when air temperatures fall below 50°F (10°C).

If these tests yield no results, or if you still feel uncomfortable with your heat pump’s performance, you should call your licensed heat pump professional. Feel free to leave a comment below if you have any questions or concerns regarding issues with your heat pump. We at AquaCal would love to help!

This Post Has 127 Comments

  1. The display is only partially lit up ( cooling indicator and a couple random lines ) and will not change when I swipe to unlock. I turned breaker off and back on after few minutes and no change.

    1. Hi Brandon,
      It sounds like you need a new display/control panel. Please call us at 727-823-5642 if you would like to discuss over the phone.

      AquaCal Tech Support

  2. My message said “high water temp”, I called and you told me to replace water temp sensor. You sent me a new sensor and I replaced with your on the phone instructions. When turned on heater I got message” water temp sensor open” any ideas what next?

    1. Good Afternoon Mr. Ascione,
      Hope you are doing well.
      Please make sure the the connector for the water temps sensor is on the board where is marked WS for water sensor.
      Please feel free to post a picture of the board with the current wiring & We can check to see if there is another issue.
      Robert Brown
      Technical Support

  3. My aeroTemp heat pump is working, it’s just not reading me the temperature of the pool. How do I fix that?

    1. Good Morning Mr. Mercogliano,
      Hope you are doing well. We built several different models of the AeroTemp line. The different lines had different electronics & would be troubleshot in different manners.
      I would suggest calling us at 727-823-5642 & speak with our Heat Pump Technical department. We can determine what type of AeroTemp you have & move forward on getting this to work.
      Robert Brown
      AquaCal Tech Support

      1. I had the fan motor and relay replaced last year on 3-2-2021 by your service tech Scott beacon he did an excellent job but now the fan motor has quit already will not run replaced the run capacitor but still does not run what kind of warrenty is on the fan motor

        1. Hi Timmy,
          Parts come with a 1 year warranty, but there could be several reasons why the fan is not spinning; fan relay, micro-processor board, fan motor, etc. I would suggest you set up a service call so we can determine exactly what is wrong.

          AquaCal Tech Support

  4. Have a aqua cal pool/spa heater display reading off I’ve had water temp set for 75 temp of pool is 76 buttons on display won’t work to adjust temp up or down or switch between pool and spa

    1. Hi William,
      If the control panel buttons are not responding, try powering the unit down at the breaker and powering back up. If this does not resolve the issue, you may need a new display. If you have any questions, please call us at 727-823-5642.

      AquaCal Tech Support

  5. I have the pool heater heatwave model 155AHDEBNA. I does run but does not heat the water. It has flow circulating through . The air overblowing from the top is cooler than the outside air. Temperature set point is around 88F. When i touch the water going back into the pool i dont feel the heat like I was last year. Any hints I should check?

    Thank you

    1. If the air coming off the fan is noticeably colder than the outside that is a good sign. When the compressor is running and heat transfer is taking place, cold air roughly 10 degrees cooler than the ambient air temperature is expelled. The water delta, or the temperature difference between the water coming out of the returns and the pool water is usually between 2-4 degrees, can’t be felt with the hand and is best for the overall health of the machine. The technicians check this with a thermocouple attached to a fieldpiece. The pool circulation pump and filtration impact the water delta. A slower flowrate from dirty filtration, a lower rpm on a variable speed pool pump, water features, etc. will increase the water delta. Higher flowrates will decrease the water delta. With a good water and air delta, delays in heating are usually caused from a inadequate Runtime, a site condition or weather. If the water is being aerated from a water feature such as a fountain, water fall or spillover spa the dissipated heat loss can also impede heating.

  6. I have an aquacal pool heater that is about 3 seasons old. It was running fine for the past month. Right now it wont power on. The screen isnt powering on either.

    1. Hi Brian,
      If there are no lights on the heat pump you will want to check the breaker/disconnect out by the heat pump and check the breaker at your main breaker panel. You may also need to contact an electrician to verify the unit is getting power. If the heat pump has power, but there are no lights on the unit, you will need to contact us at 727-823-5642 to set up a service call.

      AquaCal Tech support

  7. I just opened my pool, and when I turned on the breaker for the tropical heat pump the display is lit up but blank. No numbers or information is displayed. Just the back light is on. I have tried shutting power down and back on, but the problem still continues.

  8. My heat pump turns on for a few seconds and then turns off. The display is not lit at all. We have checked all the breakers and they seem fine.

    1. Hi Samantha,
      You will either need an electrician to verify that power is continuously going to the unit, or a heat pump technician to check the heat pump. If you would like to set up a service call, please call us at 727-823-5642.

      AquaCal tech Support

  9. I have Tropicale 115 ahdsbtd wired with a 2 wire pentair automation it shows its getting signal from the controller but the unit wont turn on.

    1. Hi Amber,
      If you have a Pentair automation system controlling your heat pump and the heat pump will not turn on, the issue could be the Pentair automation, the communication wires, or the heat pump. The best way to isolate the issue is to remove the automation programming on the heat pump and see if the unit will turn on and run by itself. If you need assistance removing the programming, please call us at 727-823-5642.

      AquaCal Tech Support.

  10. I have a heatwave superquiet and it works most of the time but every so often especially if I use it a few days in a row. The fan will run but the compressor never turns on. Any suggestions?

  11. Hello, just puts chase and installed the Aquacal T090. It has the “No Pool/Spa water flow “ message. Based on the manual I adjusted to flow valve but nothing. Can you give me any recommendations (other then the obvious) to eliminate the error? Motor is on and water is flowing back into the pool as usual.

    Thank you,

    1. Hi Ruben,
      If you have a cartridge style filter, try removing the cartridge filter from the canister, put the canister back, and run the circulation pump to see if you still get the flow message. If the message goes away, you will need to replace the cartridge filter. If you still get the flow message, please call us at 727-823-5642.

      Mark H.

    1. Hi James,
      If you are sure the unit has the correct voltage coming in (220V), but there are no lights, it could be a bad display. There are other components that could cause you to not see any lights, I.E. transformer. The display is replaceable. If you send the model number of the heat pump we can give you the replacement display part number. If you have any questions, please call us at 727-823-5642.

      Mark H.

  12. Hi,
    Aquacal model: 090AHDSBTF.
    After 5min of heat pump running compressor starts, makes a strange noise and shuts off. Pump itself is running. Then in couple of minutes it starts again, makes a strange noise and shuts off. it goes on and on and on. No warm water pumping in the pool.
    Do you guys have a video or procedures on what needs to be check in (on) compressor?
    Thank you,

    1. Good Afternoon Tony,
      hope you are doing well. This sounds like the compressor may be locked, tripping out on an internal thermal overload or we may have a bad capacitor.
      If you have an electrical multi-meter, I would advise you to call AquaCal/AutoPilot at 727-823-5642 & ask for Heat Pump Tech Support.
      We can guide you through what to check & help narrow down the issue. We are available 8am – 5pm Eastern Monday-Friday.
      Robert Brown
      AquaCal – AutoPilot Tech Support

  13. I have an ACT 1250 heat pump. Fan is running fine but the compressor doesn’t want to kick on. It tries every few minutes but never comes on. No error messages. Flow is fine. Any ideas? Help!

    1. Hello Jonathan,
      If the compressor is not starting it could be something simple, like a capacitor or something complicated like a compressor. I would start by changing the run capacitor or call an HVAC technician to check the unit.


  14. My inground pool heater is a aquacal, and the display says ota. After researching it, I found I need a new water temp sensor. I don’t know where to buy one as I called 10 pool places around here and nobody carries parts and does the heat pump work if I unplug the old sensor.

    1. Good Morning Dan,
      Hope you are doing well.
      The heater cannot run unless it can measure the water temperature. This is per government guidelines for public safety.
      If local dealers cannot source the part for you, I can recommend the online company as an authorized dealer.
      The part number to request is ECS0275.
      Please feel free to call us at 727-823-5642 with any further questions.
      Robert Brown
      AquaCal Tech Support

  15. Hello,
    Noticed my pool heater had no power recently. It is a Sure Quiet Heatwave. I checked the breaker and it was tripped. I reset the breaker and had power. When the compressor started the breaker tripped again. The unit is only about a year old. Any help would be greatly appreciated. Thanks

    1. Good Morning Mr. Smith,
      Hope you are doing well. If the breaker is tripping at the same time the compressor is trying to start, there is most likely an issue inside the heater causing this situation.
      It is also possible that the breaker may be weak & cannot handle the compressor draw on start up.
      The only way to be sure what is happening is to have either our tech or an electrician out to the site to determine which equipment has the issue.
      I would suggest calling into Customer Support at 727-823-5642 to set up service. Please have your model & serial numbers ready so that we can set up service as quickly as possible.
      Robert Brown
      AquaCal Tech Support

  16. I just opened my pool and turned the heater on overnight. Temp was around 65 degrees overnight. I set heater to 82 degrees. When I checked it in the morning the bottom of the unit had frost on it. All around the bottom of the unit. In fact I look inside and saw frost on the lines as well. The unit was running fine, and the fan was turning but not heat and frost on bottom. Help

    1. Hi Philip, a little frosting can be normal in cooler morning temps. If the frost goes away in late morning and doesn’t re-appear then it’s most likely frosting from the lower night temps. If you don’t feel this is the case, please contact us at 727-823-5642 to have service.

  17. Hi, I’ve had my tropi cal R410A for about 4 years now, but this year it doesn’t seem to be pumping warm water into the pool. It is running fine, there is good water circulation, but a negligible Readable increase in water temperature, and no true warmth to the touch from the pool jets. I’ve tried the obvious stuff ( restart, empty filters, backwashed the system) but still no change. Is there something else I can try?

    1. Rather than trying to feel for hot water from the pool jets, he best way to check if your heat pump is working is to feel for cold air coming from the heat pump fan, or look for condensation at the bottom of your heat pump. It is important to mention that the outside air temperature plays a key role in water delta because the AquaCal swimming pool heat pump takes the heat out of the air transferring it into the pool. Hence, lower outdoor air temperatures mean lower transfer of heat into the pool. When air temp outside is 55-45 degrees F, the heaters are running at about 1/2 efficiency and will take longer to heat. Also drops in air temperature over night without a cover will negate most heating done while the system was running. If that’s the case, is recommended to run the heat pump for 24 hours until you reach the desire temperature.

  18. Hi,
    I have no power to my aquacal pump for my in-ground pool. Is there a fuse located in the heater. Seems like there is no electric going to the hater.

    1. Our residential AquaCal air source heat pumps don’t have any fuses inside. I would start by having an electrician confirm power from the breaker to the heat pump. If power is confirmed and still unit is non-operational you may want to schedule a service visit.
      Please feel free to call us at 727-823-5642 to discuss further.

  19. Aquacal model 075ahdsbnb
    Looking for part # for water temp sensor.
    Looked online but they all look different.

    1. Hi Ellis,
      The replacement water temp sensor for this unit is part number ECS0275. It’s a different style sensor than the one currently in place. If you have any questions, please call us at 727-823-5642.


  20. Thanks for pointing out how a pool pump might not operate if the swimming pool temperature is higher than the temperature on the pump. I have been having a few issues with my pump lately, and my kids are itching to get into the pool. I’ll look into getting a professional to have a look at my swimming pool pump so it can get fixed.

  21. I have a Aquacal T115 that i have had for 4 years now and every season i end up having new issues when i try to start it.
    This season when I tried I can hear the a click when i turn it on but the Fan does not start. a few minutes later I can hear the heat pump turn on. I have changed the capacitor for the fan but it still will not star. Has anyone else had this issue?

    1. Good Morning Mr. Peiper,
      Hope you are doing well. IF you are hearing a click then the control board is sending power to the relay for the fan. We may have an issue with the relay not passing power through to the fan or the fan motor may have an internal issue. Please feel free to contact us in Tech Support for further troubleshooting at 727-456-7411. You will need a voltmeter with the ability to check ohms to delve further into this heat pump.
      Robert Brown
      AquaCal Tech Support

      1. Good Morning Mr. Pedraja,
        Hope you are doing well. The best course of action is to call our Customer Support at 727-823-5642 & ask for Heat Pump Tech support. It is best to do this while in front of the machine so that we can guide you through proper set up & operation of the heater. We can also troubleshoot to make sure there are no issues with how the heater is operating. We are available 8Am-5Pm EDT Monday through Friday.

    1. Hi Alex,
      Hope you are doing well. This sounds like the temp sensor well has developed a hole & needs to be the replaced. The parts number is STK1113A.
      Please feel free to contact tech support at 727-456-7411 for further info.
      Robert Brown
      AquaCal Tech Support

  22. Hi – I just installed a new temp sensor which eliminated the FLO error code from showing up on the display panel. Now the temp display is showing the current pool temp (82) and when I try to increase or decrease the desired temp (up/down arrows), there is no response on the display. Only the current pool temp showing. Any guidance on this issue? Thanks! Model is T-115.

    1. Hi Bill,
      If your display has a mode button, make sure the unit is in “HEA” mode. There could be an issue with the display/control panel. Please call us at 727-823-5642 and we will be happy to assist you.

  23. My 12 year old Aerotemp heat pump fan stopped spinning the other day. The fan spins for 3 seconds and then stops. Do I need a new fan motor or just a capacitor.


    1. Hi Bill,

      Hope you are doing well. If the fan starts, then the issue is less likely just a capacitor as that is the capacitor’s only job.
      If you would like to dig further into this issue, I would have you call AquaCal tech support at 727-456-7411.
      Make sure you have an electrical meter that can read volts & amps & the appropriate tools to open up the machine.
      Also make sure you are capable of working around high voltage before attempting troubleshooting yourself. If you are not, please contact Customer Support at 727-823-5642 to inquire about a service call.
      Robert Brown
      AquaCal /Autopilot Tech Support

    2. I have a aqua cal heater.. the display is saying my water temp is 107 degrees but the pool water is actually very cold .. I have the desired temp set at 80degrees. I don’t believe the heater is getting a correct temp read.I cleaned the filter and pump basket .. I don’t believe it’s a FLO problem .. do you think it’s the something in panel

      1. Hi Chris,
        More than likely the water temperature sensor will need to be replaced. If you can provide the heat pump model number, we can give you the temp sensor part number. Please call us a 727-823-5642 if you have any questions.


        Mark H.
        AquaCal Tech support

  24. I have a whisper quiet unit. First startup this year, no codes, water in is 61, asking for 80. Panel shows proper set point, fan is spinning, red light indicates heat. Every 5 minutes there is a hmm, compressor trying to start??, then nothing. Capacitor problem? Frozen compressor? Next steps for troubleshooting? Thanks.

    1. Hi Jim,

      Hope you are doing well. Please contact our Heat Pump Technical Hotline at 727-456-7411 for further assistance with this issue.
      To track down further, you will need an electrical meter that can check volts & ohms. If you do not have this on hand, you can call 727-823-5642 to set up a service call with customer support.
      Robert Brown
      AquaCal Tech Support

  25. my heater says flo but all my valves are set correctly, and filter and basket are both clean, where else could the issue be i only have 2 pipes, one goes in from filter the other comes out of heater to spa/pool and under normal op without using heater, water flows just as it should, i thought maybe it was connected to my salt generator and that the flow sensor was bad but after bypassing the sensor my salt generator shows flow is fine but i still get “flo” on the heaters screen.

  26. Hi,
    Working well since 2012, my Heat Pump Aquacal model 035 deliver me a strange error code.
    This code is “OtA” (Not OTA).
    Yesterday, first day after winter stop, working well (Pool water t°: 66°F, Outside t°: 75°F, Flow ok, Desired t°: 82°F, no additionnal heater)
    Today the pump does’nt start, (no fan) with this code OtA.
    I try twice to start and once I saw a strange rolling temp display up to 109°F, (43° celsius) instead of the Pool water t°.
    What happen?
    is there a service center in France?
    Cordially, Michel from France

    1. Hello Miched,
      OtA stands for “Over Temperature Alarm” meaning the heat pump believes the water temperature is 110 degf. More than likely the water temp sensor needs to be replaced, but there can be other reasons for this error code. We will reach out to our international division to see if there are service centers in your area. They will contact you via email.

      1. Hi,
        Thanks for your quick answer,
        If I have to change the temperature sensor it would be necessary to have a broken plan of the pump, that I can locate the location of this probe and its reference to order it.
        Where can I find it?
        I guess the water temperature sensor is the one which is located on the inlet piping, as I can see it (there is a second sensor on a copper pipe) In the absence of repairman I have to change it myself, but this probe seems sealed, is that correct?
        is there a special procedure to disassemble it?
        Thanks again

          1. Hi,

            The sensor is: Aquacal Heat Pump Water Temperature Sensor ECS6105 10K 0HM
            To remove the doubt I inverted the two probes on the electronic board because I found that the Water sensor is the same as the Defrost sensor
            The pump has started so it confirms that it is the water probe that is failing.
            I found a replacement kit that allows to leave the faulty probe in place (to avoid any breakage):
            AquaCal ECS0275 / STK0127 Water Temperature Sensor replacement Kit:
            Just drill a hole
            – Use 11/32″ or 3/8″ drill bit to tap into water inlet line.

            – Snug the hose clamp around the sensor.

            Maybe this information can help somebody when there is no repairman

  27. I have an aquacal model 135, the digital controller is not increasing water temperature, it is reading the water temperature in pool, unable to increase temp to 86, can lower but still fan not coming on, please help, I am frustrated since I purchase this heat pump I only use it between 5 to 7 times

  28. My heat pump the desired temp is at 78 but the temp of the pool per the heater unit is 102. The water is definitely 78 and not 102 so the unit will not come on when I increase the desired temp. What would cause this?

  29. I have an older heat pump, aerotemp tempro 2000. Unit ran fine and heated well until one day it would not turn over. It has power, when pump is off says flo (so I’m guessing at leaSt some of the sensors work to throw that code). When pump is on it displays the temp like it normally does, then after about 1-2min (which is how long it used to take for fan and compressor to fire up) instead of firing up a small red light appears on panel in between the orange indicator lights of pool and spa.I did have someone come look at the unit and they said temp sensor and very low on r22, could the low r22 cause this and not put up some kind of error code? I don’t think the temp sensor is bad as it seems to acurrately display the temp of the water passing through unit just the fan and compressor don’t fire up so I get no heating… it did randomly fire up one day, which was a couple of days after I had messed with the unit and apparently left the breaker on, then the next day same thing, wouldn’t fire up.

    Any thoughts or assistance is greatly appreciated!

    Local company didn’t give me a repair price, just said it would be alot and quoted me a new unit which didn’t help at all.

  30. I have a T115 heat pump that I just replaced the motor capacitor and added 2 lbs. of R22 freon (yes it is old analog unit). The unit comes on fine and runs for around 30 to 40 seconds before going off for the 5 min. restart and then it repeats itself. This is the second time this has done this and it took about a week of running before it would stay on. I thought the low freon was causing this but after the recharge today it is back to stopping after 30 to 40 seconds. I live in Lutz, FL. (Tampa).

    1. Hello Leo,
      There are many things that could cause the your analog unit to shut off. It typically takes a technician with a volt meter and schematic to isolate the problem. Please call us at 727-823-5642 with questions or to set up a service call.

  31. We have an aqua cal pool and spa heater and it’s not getting power to it. We are planning to replace the breaker and see if that’s the problem. Is it necessary to replace it with a breaker with a ground wire?

  32. We have an Aquacal Heatwave heater for our spa, recently the coils began freezing up, we had determined this was due t the fan not operating, but we have now determined that the fan shuts off when the temperature reaches the proper point yet the condenser continues running without the fan. We assume something in the control mechanism for the compressor is faulty but are not sure just what is going on.

  33. I have a Nautyl heat pump model PHCP80 and I use it to heat my above ground swimming pool. Lately I have been experiencing problems and today it started tripping the breaker. Wondering if you can help me out with this problem. When I turn it on, it will start normal, then the compressor cuts in, and about 10-15 secs later, the breaker trips. Have you seen the problem before and if so can you help me out?


    1. Hi Dion,

      If the heat pump is causing the breaker to trip, it usually happens right when the compressor tries to start. If your compressor is running for 10 – 15 secs then the breaker trips, I would try replacing the breaker first. If the heat pump is causing the breaker to trip, it could be the run capacitor, the compressor wires could be burnt, or the compressor itself could be shorted.

  34. This is a new question about a Jandy Lite2 (LG175NG).
    The pilot will stay lit and when I jumper TH to PP-TH the boiler runs fine.
    I have gone through all the testing of the millivolt system and here is where I get stuck/confused.
    At the end of the black TH wire I have 520 millivolt. When I attach the wire to the TH terminal and the test at the terminal I ONLY see 48 millivolts.
    What could be going on here?
    What could be wrong here?
    Thanks for any help.

  35. I have a Tropi Cal T115. Just had to replace the fan capacitor and now the display reads OtA. The water temp is 75 and the pump is set to 88. This error will not clear after. Overnight water temp drops to 72 and pump still won’t come on. Please advise

    1. Hi Daniel,

      OtA stands for Over Temperature Alarm, meaning the unit is measuring the water temperature at 110 DEGF. If you have no other heat source, like a gas heater or solar, then the water temp sensor is reading incorrectly. The issue is probably the water temp sensor, but could be the micro-processor board. Please call us at 727-823-5642 and we will be happy to assist you.

    1. Hello Diane,

      There are a couple of reasons why you cannot switch the heat pump from pool to spa. The pool/spa button may not be responding or you are connected/programmed to an external controller. Please call us at 727-823-5642 to discuss.

  36. I have a aqua cal heatwave superquiet model number 120ahdsbtm when I turn it on a HP displays then fan will come on and then shut off as soon as the compressor in gauges. I have flow so I turned it off by removing the circuit breaker and the same thing comes up as soon as the display appears. Any suggestions

    1. Hello Victor,

      If the “HP” message occurs immediately when the unit is powered up, you will probably need a service tech to check the unit. Please call us at 727-823-5642 and we will be happy to assist you.

      1. Good Afternoon Steve,
        Hope you are doing well.
        There are several issues that can keep a unit from starting up. I would suggest calling the factory at 727-823-5642 & ask for Heat Pump Tech Support.
        We can troubleshoot over the phone while you are at the heater & see what is happening.
        Robert Brown
        Tech Support

  37. We have a Aquacal Heatwave Superquiet, it is roughly 4 years old. I am getting an F5 error code on our display. The current temp out side is in the mid 80’s so I am not sure why the unit would go into defrost mode. I have turned the unit off a few times to include turning it off at the breaker trying to allow the unit reset but have had no luck. Do you have any suggestions?

    1. Hello John,

      Insufficient water flow can cause the “FLO” and “HP” error messages. Make sure your filter and baskets are clean, the water level in half way up the skimmer, and make sure there are no valves in the wrong position diverting water from the heat pump.

  38. I have a aquacal heatwave model#100ahdebna and the control panel doesn’t lite up. How can I test university with out the control. I would hate to spend the money and that’s not the issue with unit. I want to make sure unit works before I spend a few hundred dollars on it.
    Is there a way to jump the control board. I’m a plumber I should have necessary tools to perform work

    1. Hello Lazaro,

      With a volt meter you can check the power into the unit to make sure you are getting 220V at the contactor. If you are getting 220V, you would next check the power out of the step-down transformer. You should be getting around 26V (AC). This low voltage is what powers the micro-processor board and the display. If you are not getting 26V you probably have a bad transformer. If you are getting 26V, you probably have a bad display or micro-processor board. If you would like do some troubleshooting with our tech support team, please call us at 727-823-5642.

  39. My Aqua Cal seems to be working but the display is blank. Maybe a burnt out bulb? Can’t tell what temp anything is. What do I do?

  40. Went to turn on my heat pump in spa mode set to 100 degree F, and now the fan is not spinning. Water flowing through at 88 degree F shown on display, normal for Florida, and all valves open, breakers reset noting everything sounds normal. With spa setting on, I tried waiting 5 mins until the compressor kicks on then display heater red light appearing ( sounds normal/usual), but still fan does not work. Top of fan warm to touch. Everything sounds normal without fan spinning. Aqua cal Model H155.
    Is this a fan motor / capacitor issue, or other problem.? Can you help me problem solve this issue?

      1. Good Afternoon Mr. Shumway,
        Hope you are doing well. There are numerous reasons that could keep your heat pump from starting. The best advice I can give is to contact our Tech Support Department at 727-456-7411 while you are near the machine so that we can troubleshoot this for you.
        Robert Brown
        Customer & Tech Support.

  41. Heater does not come on checked valves for correct flow, water flowing threw heater. Heater still reads FLO
    Pulled panel wires and connections look good. Heater has power. Please help!

  42. new heater. set temp to pool on 90. Heater turmed on then one minute later turned off says 79 on display. Water Temp 79. Wont turn back on to heat pool. Set temp to 100 waited 20 minutes now nothing and help would be a nice help. Tech support has been busy for some time now.


    1. Good morning Mr. Jacobs,

      Sounds like you need to have someone come and look at your unit (which is still under warranty since it is new) Please contact our tech support department, if you are still having problems getting through, you can email your contact information to and we will have someone contact you directly.

      Thank you!

  43. heat pump does not start. Checked everything: mode = "heat", "pool" selected, set temp > pool temp. there are no error messages, e.g. FLO is not lit. Is there something simple I am overlooking or could check? TropiCal Model 115

    1. Good afternoon Dave-

      Please contact our technical support department at 727.823.5642, they will be able to help you as your unit is analog.

      Thank you!

  44. During dormant season pump develops issues. This year it doesn't seem to heat although it runs. Beyond the latter issue, it register water temp as 101 when actual temp is in the 60s. Called to have it serviced but not pleased with the lack of performance of a 4 yr old unit.

  45. I just turned my heat pump on a couple hours ago…. it said LP… I checked all connections… and everything is fine. Then it turns on, but the heating light does not come on!! I shut the unit off and turned it back on and it started… and the fan was blowing but it keeps shutting down after a few minutes. The heat light came on for a few seconds and then the unit shut down again. Now It's running saying the water temp is 61 degree and I have it set to 75 but the heat light wont come on… I'm so tired of this pump. Please help me

    1. Hello Michael,
      An LP code indicates the low pressure switch on the refrigerant circuit has opened. Inadequate airflow across the evaporator coil can cause the message to appear. Other than that, this code will require a qualified service technician. Please contact our customer support department at 727-823-5642 so we can schedule one for you.

      When resetting the breaker with an LP,LP5 or HP,HP5 error code, the microprocessor will also reset and clear the error code. The fan will come on and spin as normal. There is a 4 minute time delay for the compressor to engage. Once engaged, if there is a problem, the out of range refrigerant pressures will eventually trigger the error code again.

  46. I have an aqua cal model tt120a-a ser# 1023945-f03. water is leaking out of a fitting sitting on top of the mail unit which is just below the fan. it has two small wires going to it. with the unit off & the pool pump on, water comes out of this fitting. what is this fitting and can I change it? Is the pool pump too old & will this cost too much. I don't use the pool pump more than twice a year. thanks. I have been trying to call at 800-786-7751 and can not anybody.

  47. Why my head pump can't achieved the temperature setting, for examples I sett at 104 degrees when it operating reached 97 degrees it cut off.pls advice.

    1. Good morning Ray-

      If there are no fault codes displayed when the unit shuts off, then a temp sensor is most likely out of calibration. You would need a technician to rectify this. You can contact our tech support department by following this link:

      Please feel let us know if there is anything else we can do to help!

  48. Good morning Lisa-

    We will be happy to look into this issue. We need more info to do so. Name, address and phone number, model and serial if available. Who has been doing the work on the unit?

    With this information we will be able to follow up.

      1. Good morning Paul-

        Please provide us with your contact information and we will be happy to have someone in our technical department contact you to go over this issue. You can also forward this information to if you rather not post it on this forum.

  49. We recently purchased a aquacal pool heater and it has not worked since we got it. Keeps saying LP. The valve has been changed out twice in 2 weeks. Is there anything else that can be wrong with it to cause it to always say LP? We are not happy with product and for the price we paid, we cant go through this any longer. Why have it take up space on our property when it does not work..

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