amblie

Hayward Hayward 'LO' code

amblie
July 14, 2008

I'm getting an "LO" on my heater and the service light is on. Any ideas?

Comments (70)

  • PRO
    Hayward Pool Products

    Amblie, we'd be happy to help. Please PM us on Houzz - our Hayward tech will call you. Thanks.

  • oc2347

    Lol please tell me how to PM you on Houzz.

  • PRO
    Hayward Pool Products

    You can message us via the "Contact Me" link on our Houzz page.

    Here's what our Hayward tech shared: LO indicates the pump is off (normal) or the flow has diminished and the pressure switch has not closed indicating low flow. The most common reason is a dirty filter (clean the filter). There could also be a stuck by pass valve in the header or someone closed an external valve cutting off flow to the heater. If the pump is running and none of the reasons above exist, it's most likely a bad pressure switch.

  • degrandpre5

    I just found this post. Just to be clear, if LO is showing on my display and the pump is off, that is normal. It's only a problem when the pump is running and the LO is showing?

  • PRO
    Hayward Pool Products

    Thanks for your question. We'll ask our tech for his reply.

  • PRO
    Hayward Pool Products

    Tech reply: Yes, that's correct.

  • loretta_michaels

    I'm having the same issue with my new pool and heater. It wouldn't ignite and kept showing LO, and the gas people said it wasn't their issue, while the pool people said it was a gas issue. Anyway, gas people came out and upped the gas rate, which seemed to do the trick. Now the heater works, when the pump is running, but when the pump stops it reads LO and the service light is on. Why would the service light be on if this is the "correct" response? (And why get an error code at all??) Thanks.

  • PRO
    Hayward Pool Products
    LO means the limit string is open. Most likely culprit is the pressure switch. If LO appears while the pump is running it most likely is a water flow problem. This is a dirty filter 90% of the time. LO on the heater when the pump is off is normal.
  • loretta_michaels

    Thanks! In fact, I removed the cartridge filter (which wasn't dirty - it's brand new) just to see if that wasn't the problem. At this point, there's no cartridge, so that's not causing a blockage. Is there just one pressure switch that needs to be checked, or multiple? And should I be concerned about the service light being on?

  • loretta_michaels

    And while I'm here - what on earth is the "limit string??" The owner's manual mentions this as well, but doesn't say what it is! (Who writes these manuals??)

  • PRO
    Hayward Pool Products

    The limit string is made up of the high limits (normally closed), the water pressure switch (Normally open until there is water flow) A vent pressure switch (normally closed and only in play if the heater is inside with a vent pipe installed) and a flue gas temperature switch (normally closed senses flue gas temps in case they are too high). All but the water pressure switch (WPS) are closed. This makes the WPS the likely culprit when the LO appears. Since this is a gas fired appliance we strongly recommend that it be worked on by a qualified tech. Manuals are written for appliances like this to allow the technician to follow the path for troubleshooting.

  • loretta_michaels

    Thanks very much for the answer! One more quick question - where is the WPS? I can't seem to find it in the manual drawings.

  • PRO
    Hayward Pool Products

    On page 30 of the installation and service manual you will find the diagram. In the upper right hand corner is the switch. Loretta, please private message us with your phone number if you have additional questions. Thanks

  • loretta_michaels

    Just a final follow up on this thread, as someone was asking me how we sorted out our problem. After much frustration and finger-pointing between our pool guy and the propane gas guys, with the heater constantly shutting down and showing LO after 5-10 minutes, we finally got hold of a regional Hayward tech manager. He said it was nothing to do with the gas, suspected poor water pressure, and planned to come out to visit, but in the meantime suggested we close off one of the eyeball (?) outlets in the pool (we have 3), in order to increase the "back pressure" (?). I did that and lo and behold, the heater works as intended! At this point, we've closed down the pool for the winter, but in the spring we'll either keep one of the 3 outlets closed, or he suggested we adjust the pipe handles to also increase the back pressure. We'll play with both and see what works best. Just throwing that out there, as it took us ages to find someone who understood the issue. Our pool guy hadn't heard of this this at all.

  • PRO
    Hayward Pool Products

    Loretta, let us know how your pool start-up goes in the spring and feel free to reach out to us for tech assistance anytime.

  • Branden Mullins

    I have a LO code and I have replaced all circuits boards pressure switches and anything related as well as the filters and have correct pressure. Still LO. Literally have replaced everything. Please help

  • PRO
    Hayward Pool Products

    Sure Branden, happy to help. Please PM your phone number and we'll ask a tech to call you to assist.

  • Willie D

    I also get the LO code when the pool pump is running, the service light is on and the blower on the Hayward heater runs when the pump is off. I have a DE filtration system andthe pressure is around 14 psi, so I believe it is ok.

    Any ideas why the blower fan runs when the system is off?

  • PRO
    Hayward Pool Products

    Willie, our tech is happy to help. Please PM your phone number for a call back. Thanks.

  • Willie D

    OK I just sent a response through your website.

  • PRO
    Hayward Pool Products

    Got it, thank you. Our tech will give you a call.

  • jdthreemom

    I am having this same issue for LO on the pool heater. How do I reach a pool tech

  • PRO
    Hayward Pool Products

    Happy to help! Please private message us from our Houzz profile and a tech will call you.

  • mrol1959

    I have a 400 Hayward. Shut gas off for winter and turned back on. Unit goes to LO. Tried power reset, checked all circuits and showing closed while pump is running. Water, 2 air, 2 thermistor for total of 5/ I have voltage across all as well as jumped them. Still get service and LO. Is there a master reset or hard? Breaker has been turned off as well and reset

  • PRO
    Hayward Pool Products

    Hi there, please private message your name and phone number and our tech will be in touch.

  • PRO
    Hayward Pool Products
    LO on the heater is an indicator that one of the high limits or pressure switch is open. When the pump is off the LO is a normal reading. If the pump starts running and the LO does not go away there is a problem but it may not be the heater. The most likely cause is a dirty filter causing low flow so the pressure switch will not close. Also any valves that or still closed.
  • dianekuepper

    Good morning - I had a pool heater recently installed and it has consistently shown the LO code and the yellow warning light. The longest it has consistently worked is 5 days. Not sure if it is a problem with installation or the unit or something else.

    Any advice? I am fairly chicken about working with the unit :)

  • loretta_michaels

    See my comment above from Dec. 28 - water pressure seems to often be the culprit (and every time I called the help line they said to see if the filter was clean, which WASN'T the problem). Good luck!

  • PRO
    Hayward Pool Products

    We are always happy to help. Private message us on our Houzz profile with your phone number and a tech will call to help.

  • Cool Kids

    Have the same issues with LO code. I’m located in Canada - need help finding a Hayward tech. I’ve sent in my details in a PM on the site.

  • PRO
    Hayward Pool Products

    Hi there, Here's a link to our Dealer Locator in Canada: https://www.hayward-pool.ca/shop/en/canada/Locator?langId=-1. If you'd like, our tech can call you. Please provide your phone number.

  • PRO
    Hayward Pool Products

    LO is normal with the pump off. If the LO code stays with the pump on there is most likely low flow into the heater. Most likely culprit is a dirty filter. Could also be a bad pressure switch or high Limit.

  • stylesense
    I have the Hayward 1.65 thp Model M48AB20A04 (2 years old). The variable pump is stuck in 50% mode and I’m not able to manually increase/decrease the speed above or below 50%. The only time I can get the pump to flow higher than 50% is when I turn on the Hayward heater and it automatically goes to 75% flow.

    I have not manually changed or adjusted any settings on the main control box.
    Has anyone else had this issue/fix? Can a Hayward tech please help?
  • PRO
    Hayward Pool Products

    Hi there, our tech would be glad to call to help. Please PM your name and phone number.

  • PRO
    Hayward Pool Products
    Sounds like you have a controller that controls the pump. The fact that the pump will go higher when the heater is used tells me the problem is with programming within the controller.
  • Shahed Islam

    We got a new Hayward H150FDP Universal H-Series Low NOx 150,000 BTU Propane Gas Residential Pool and Spa Heater and after following direction getting LO error. Water pressure is showing green on pool pump, checked propane gas tank and gas is coming. Since it’s a new pool no clogging also. Do I need a big propane tank ? Where I can get help to fix this

  • PRO
    Hayward Pool Products
    Hi Shahed, our tech would be glad to call to help. Please PM your phone number.
  • scurlow

    My heater is a Hayward H400FDN and I tried to start it up this spring and it does ignite, but shuts off and gives me the "LO" code. Could this be a flame sensor issue? My filter was just cleaned.

  • PRO
    Hayward Pool Products
    LO normally means the water flow through the heater is inadequate. Cause could be a dirty filter or a valve not positioned correctly. Not sure what else is happening. LO is not a flame sensor. Post a phone number and someone will call to help on Monday. Remember, LO is normal when the pump is off.
  • HU-582860505

    Have a Hayward heater that the blower will come on for a few seconds then turn off then back on and back off continually. This is with the pump off, no water flow, heater is in the off position. I was talking with a Jandy rep (because it is connected to a Jandy controller), he said that maybe the spa side controller was bad, but I disconnected it completely from the system and blower still kicks on then back off, over and over. Now when pump is on and heater is on and a call for heat is initiated it works fine no problems. Any help would be greatly appreciated. Thanks. Ron

  • PRO
    Hayward Pool Products

    If you’d like to speak with someone, please PM your phone number.

  • HU-582860505

    new to this, how do i PM you

  • HU-976529087

    We got a new Hayward H150FDP Universal H-Series Low NOx 150,000 BTU Gas Residential Pool and Spa Heater and after following direction getting LO error. Water pressure is showing green on pool pump, Where do i get help to fix this?

  • PRO
    Hayward Pool Products

    Please PM your phone number and someone will call you, probably tomorrow.

  • PRO
    Hayward Pool Products

    LO on a new heater normally means inadequate water flow through the
    exchanger. Not knowing more about your equipment, it is hard to find a
    cause. Check to make sure all valves are open properly and the pump, if
    two speed or variable speed, is at a higher speed.

  • HU-888348989

    I keep getting a LO code? So far changed flow switch and high temp sensors. Back washed filter several times. I can get it to run for about 45 minutes and then the LO code appears? Any Ideas. Thanks,

  • PRO
    Hayward Pool Products

    Please send your phone number by private messaging if you'd like someone to call or someone will reply here.

  • HU-454436729

    When you say the LO code is usually caused by a dirty filter, which filter are you referring to? The pool filter, or is there a filter in the heater also?

  • PRO

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