Laars Lite run issues

May 21, 2015
4
Derby, New York
I have a Teledyne Laars Lite LLD325N heater. I am having issues keeping it burning. I did just replace the the bypass valve in the inlet/outlet header. The old one was stuck partially open and all corroded. I all replaced both high limit switches. Prior to doing this it would run for 12 mins and shut down and try retiring 2 more times. After the parts change now it will run for approx 24 mins and shut down. Doesn't matter if I have it turn to pool or spa. The HSI appears to be working ok cuz it lights fine. And from my research this is also the flame sensor. When it tries to re fire the burners kick on for a sec then go out. If I shut it down for a few mins and turn it back on it does the same thing. Before I get into buying more parts I was wondering if anyone has other ideas for me? I've done some testing of voltages and all seems good. The sensor in the header with the plastic tube around it, is this the temp sensor? Can I bypass for testing purposes? Also the thermostat, can I bypass that to test if it's good or not? Any help is appreciated. Thanks in advanced.
 
Well thanks to the overwhelming amount of responses I got it figured out. The bypass valve in the header was stuck open. The high limit switches were bad along with the pressure switch. Little bit of trial and error and bypassing different safety parts it is now running perfect. Thanks again for your help!
 
Glad you have it figured out. Holidays are always busy times for me and usually when I get done with a days work I'm beat and don't get back to here often.
 
I know this is an old post but yet again I am still having the same issues. My heater runs for 10-15 mins and shuts down. Tries to refire and shuts down wait a couple minutes and turn it on and off and the same thing again. Tested for 24vac throughout and that seems to check out even under a load. Not sure what my options are. Could it be the Fenwal control mod? Really starting to get to me. Any and all help is appreciated.
 
Well you could really put this to rest and get rid of the old unit and upgrade it. LOL

The fact that the unit actually lights and runs for 10-15 minutes, I would have to guess that it is over heating and shutting off. Is there adequate water flow thru the unit?
 
I have the same heater and it does not display the water temperature. Mine did the same thing until I increased the dial that controls the temperature. It's possible that the temperature of the water was warmer and why it turned off.
Mine works but makes a popping(like popcorn popping) sound while heating the water. I'm getting it checked out soon.
 
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