dbrucegrant

It's taken some time to get back to this, but as it turns out the brass(?) posts that sit behind the hi-limit switch had corroded away, so I replaced them (created new ones from other on-hand spare parts, since last time I tried to order these they sent me the wrong thing). Replaced those posts and the high limit message went away. Of course I blew the inline fuse during testing and got a subsequent low pressure error - a few voltage tests and I knew to check the fuse. So, I replaced the fuse (about $0.60) and the heater starts up again! Thanks for everyone's help.

Hi Guys - thanks for the suggestions. When I bypass the hi limits the heater runs without issue. No knocking or banging. I had the high-limits replaced two years ago - when I open them up they are pristine - no corrosion, build-up or anything else untoward. And I measured resistance across the hi limits and it measured 0. I repeated again just for good measure. Byoass hi limits and heater works (without any banging) - re-enable them and heater works for 30-45 seconds and then stops heating. Is there anything I should/could try/test? Many thanks, Bruce.

No, it does this over and over again. Yesterday I decided to let it run on and noticed that after some number of cycles (> 15 minutes) I did get the "High Lim Sw" error.

My Jandy LX400 heats for about 30 seconds (blower starts) and then stops - no error is thrown in the console. It was working fine when I shut it down last year. After reading a number of posts I check connections, then checked the flame sensor connection and lightly sanded it to remove a bit of gunk, but that made no difference. The LX400 manual mentions a throttle strip on the burner tray to allow more air into the combustion chamber - I can't tell where the strip is or whether it make sense that might be the cause. I know I also saw mention of measuring the flow sensor current - is this possible without disassembly of some parts. Many thanks, Bruce.