I have a Teledyne Laars EG-125 natural gas heater (with pilot light ignition) for an above ground spa that has been replumbed for external heater/pump by previous owners. I was given the spa and heater/pump and have hooked it back up. Thanks to some help from this forum it is now plumbed and functional except for the heater.

When I first lit the pilot light, it lit fine. Then when I turned on the heater there was a small pause followed by a small explosion. Subsequently, the burners lit for about 30 seconds and went out. After taking the burner element out and giving it a thorough cleaning (which it badly needed) I put it back into the heater. I suspect that the gas burners were dirty and did not allow the gas to get to the pilot light. So, it accumulated until it hit the pilot light and boom.

Anyway, now that I have cleaned the burning elements thoroughly the pilot light will not stay lit. I can get it to light, but when I release the gas valve button the pilot light quickly flickers and goes out. I've tried adjusting the pilot light flame screw with no success. Also, I took the pilot light assembly near the burners apart and cleaned it thoroughly (it wasn't that dirty). This also did not help.

Any thoughts about things to check? I'm hoping to not have to call a service man unless necessary.

Thanks.

If I understand the problem you've described, it sounds like a simple little part the pilot flame heats and signals the valve to open when the temperature and water movement are correct. I cannot recall the name of this mechanism. (thermo pile - thermo coupling?) I did replace 1 on an OA Smith heater many years ago.

If you can get the exact model number of the heater you have, go to a good plumbing store, not Home Depot or Lowe's, and see what they can do. It may have to be ordered but it shouldn't cost that much. I'm thinking $20 to $50 max. Very simple to remove and replace once you recognize the part and where it functions.

There should be a bulb the pilot light flame heats when it is burning. Follow the wire back toward the button you push to light the pilot and that should be the part I'm talking about.

I found the thermocoupler. My understanding of this device is to tell the valve that there is a pilot lit so the valve can turn the gas on to the main burners. Is this correct? Would a faulty thermocoupler cause the pilot light to go out as well?

Thanks for the input. I'll try to find a new one. The one I have looks pretty old and worn. It could very well be bad.

When the thermocouple is properly heated it produces about 3/4 of a volt of electricity. This powers the gas valve keeping the valve open to the pilot.

You could also have a short grounding out the current. Or a bad gas valve.

In looking for a replacement thermocouple I've noticed that diagrams of my heater often have the part I'm looking at in my heater labeled a pilot generator.

Is the thermocouple the same thing as a pilot generator, or is there another part somewhere I should be looking for?

Thanks again to the forum readers for all your help.

Yes it is indeed called a pilot generator.

Thanks to all for your advice thus far. I purchased a new thermocouple and installed it. Now the pilot light will stay lit. I checked the voltage and it is putting out about 600-700 millivolts.

The pilot flame is a little low. When I depress the pilot light button it increases some. When I turn on the heater I can hear the gas flow into the main burners so I suspect that the gas valve is working properly. However, the burners don't light right a way. I'm concerned the pilot light flame may not be large enough to reach the main burner area. I suspect this is what happened last time when I had a small detonation.

Adjusting the pilot light screw will make the flame smaller, but not larger. Does anyone know the gas pressure needed to run this system (Teledyne EG-125)? I've got a gas line run from my meter approx. 35 feet with 3/4 inch pipe. It seems as if this should be enough to feed it, but I'm not sure.

Thanks again. Once the tub is fully functional I'll send some pics.

I've been traveling across the country and have just now had a chance to check back in and see what's been going on.

I'm glad to hear you're on the right path for a solution.

As I recall with my previous "pilot lit" A O Smith heater, I had some adjustment available for regulating the supply flow to the burners. I had them set pretty low in the summer to decrease the time it took the tub to heat and high in the winter to over come the greater temperature difference.

Mine was a rod that moved horizontally left to right. I've observed a few that have had dials.

If you have such a feature, it will be located near the bottom of the unit or near the main gas valve.

Or another thought could be a clogged supply line. I've have found bits of sand in the supply pipe, my side of the gas valve. Try disconnecting the Union and check to see if there is an accumulation of debris. If you find anything, try and blow it out with compressed air.

My new heater diagrammed a "T" fitting between the outside supply line and the Heater Point of Connection. This was to trap any sand before it could enter the heater valve. I went ahead and installed this feature between 2 shut off valves with a 4 inch nipple and cap. It's only be operating a year so I haven't checked it to see if it has caught anything.

I'm pleased you're staying with this and keep up the good work. I just love using natural gas.