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

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Poolhaven

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May 19, 2014
12
New Jersey
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
 
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?
 
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.
 

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