I have an older inground hot tub with a Teledyne Larrs EG175 heater. A few years ago I installed a brand new burner unit to convert it from Natural gas to LP. It worked great until this season. now it will light and run but it will not shut off after the temp. gets to the setting? Could this be something other than the thermostat?
Thank you,
Steve

Unfortunately, no one ever answered this. I think maybe you got it repaired anyway and didn't share the news or the cause of the problem. It was a good question. What say you.?

Unfortunately, no one ever answered this. I think maybe you got it repaired anyway and didn't share the news or the cause of the problem. It was a good question. What say you.?

Well actually I never have got it repaired. I just have not used the hot tub much and when I do I have to get out and shut off the heater. I still am interested in resolving this issue.
Steve

http://www.jandy.com/html/productsupport/#manuals

I can't find an EG manual but a lot of the heaters are similar but with different types of control boards.
Look at the LG manual on the above site. Around page 30 it shows how to test the temperature sensor thermister located up in the water jacket. and the heater control.. If this diagram is close to your model setup it won't take much to locate the problem with a VOM meter. You may want to check out some of the other manuals on that site to see if any exactly match your heater and controls circuits.
lol

Something or things are jammed in the go position or the wiring on the gas valve has been short circuited from TH to TH. Disconnect one of the wires from the gas valve that go through to the on/off , the thermostat, the hi limits and the pressure switch and back down to the gas valve (marked on a millivolt gas valve TH and TH). Test briefly to see if the heater lights now even with the pump turned off. If it does the gas valve is jammed open and must be replaced. If it didn't light , turn the pump back on and reconnect the wire to TH or TH but switch the on/off to off (the heater should not light ) if it does call a good heater technician, as the on/off has failed or has been bypassed and probably other safety devises have also been by passed which makes for a very dangerous heater. It is VERY DANGEROUS to run the heater like you do , as it will boil the water in the spa no problems. The upper hi limit is designed to stop the spa water exceeding 42 degrees celsius, I don't think yours is working the way you have described the problem. You should turn off the gas and call a qualified heater technician if the problem can't be resolved easily. Sorry but I'm not sure how to convert celsius to fahrenheit but most spa thermometers show both.