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Thread: Pool heater laars lt 400 series - ags light on but troubleshooting still not helping.

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    Pool heater laars lt 400 series - ags light on but troubleshooting still not helping.

    Hello everyone
    I've got a laars lt 400 pool heater that was working last season (am in nj and it is now spring... 4yr old son wants to go in pool but it's way too cold! Up to daddy to fix it ASAP)

    De-winterized everything this spring and all seems fine except when filter running and pool heater turned on, heater fan goes on, burners get lit, heat turns on and then within 5-10 seconds i hear 'click' sound and burners turn off and blower continues to stay on... Then burners light and heater attempts to turn on again but never does and then ultimately all shuts down

    Once the 'click' sound is heard the ags light starts blinking in red

    However if the burners actually turn on - how can issue be with the ignitor, sensor, gas piping?

    Could it be pressure switch? If I'm on the right track, how do I test pressure switch? I can't even seem to locate it - even with manual in hand ! Shux, really don't ant to have to call in pool company for this one. Any suggestions. Or guidance? Thank you SO much!

    Marc

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    Re: Pool heater laars lt 400 series - ags light on but troubleshooting still not help

    Sounds like a classic case of needing to clean the flame sensor. A piece of steel wool is best to use.
    Unknown make 18' above ground (bought used in 1999) Sparco sand filter. Hayward 100,000 BTu heater. 2 speed pump

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    Re: Pool heater laars lt 400 series - ags light on but troubleshooting still not help

    Thanks for the quick reply! I'll give it a try in the am and let you know how it goes

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    Re: Pool heater laars lt 400 series - ags light on but troubleshooting still not help

    +1 on the flame sensor. Also, if that doesn't do it, check the individual burner that directs it's flame on the sensor. That particular burner could be clogged and would keep flame rectification from occurring.
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    Re: Pool heater laars lt 400 series - ags light on but troubleshooting still not help

    Quote Originally Posted by Pool Clown View Post
    +1 on the flame sensor. Also, if that doesn't do it, check the individual burner that directs it's flame on the sensor. That particular burner could be clogged and would keep flame rectification from occurring.
    Good point!!!
    Unknown make 18' above ground (bought used in 1999) Sparco sand filter. Hayward 100,000 BTu heater. 2 speed pump

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    Re: Pool heater laars lt 400 series - ags light on but troubleshooting still not help

    Hello again

    Unfortunately, after looking at the flame sensor - it looks brand new. Despite that I cleaned it and still no change in the 'cycling' of the heater going on then after 15-30 sec i hear 'click' and then heater turns off and blower continues to run and then cycle starts again - burners turn on , heater turns on for 15-30 sec , then heater turns off and blower continues to run for 30-40 sec. This cycle goes on for three cycles the. It all stops and all turns off and ags light begins to blink.

    Hm how do i check the burner associated with the sensor? Meaning, how do I get to it? Thanks

    - - - Updated - - -

    Ps I left the flame sensor in the burner without screwing it in - while the burners were on during the time the heater/burners were on - then I quickly pulled the sensor out and noticed it doesn't look 'hot'. So perhaps u are right about that particular burner. Or is that assessment incorrect?

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    Re: Pool heater laars lt 400 series - ags light on but troubleshooting still not help

    No suggestions? might just need to call serviceman. Shux.

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    Re: Pool heater laars lt 400 series - ags light on but troubleshooting still not help

    Did you ohm out the sensor to see if it is good?
    Paul
    http://www.gastekservices.com A word of caution: When working with gas and electrical you might want to consider a licensed contractor. Consider the value of your life and others around you. If you would like to provide a review of the help I provided, please use the following link to leave a review. gastek - Google Search,

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    Re: Pool heater laars lt 400 series - ags light on but troubleshooting still not help

    I am still thinking it is related to the flame sensor. When the electronics in these heaters allow the gas valve to open they essentially allow the heater to run in a mode that bypasses some of the safety features (flame sensor) for a set amount of time. Usually about 10 seconds. This is to allow for the flame to establish itself and be present for the sensor to "see" it. If the flame sensor proves good then the control board will allow the valve to stay open. If not, it will shut down and try again for a pre determined amount of tries. Usually 3. If you were able to get to the sensor to clean it you should be able to see the burner associated with it. Since flame sensors rarely ever go bad (other than needing to be cleaned) I am going to guess the burners need to be cleaned. There could be a spider nest in the tube that feeds the burner head or rust/other debris blocking the gas flow in that area.
    Unknown make 18' above ground (bought used in 1999) Sparco sand filter. Hayward 100,000 BTu heater. 2 speed pump

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    Re: Pool heater laars lt 400 series - ags light on but troubleshooting still not help

    The burner tube appears to be large or am I looking at just the initial opening?

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