Gas Water Heater Won't Stay Lit

somefun · 06-14-2009, 02:39 PM

My gas water heater, an Atwood G10-2, won't stay lit long enough to heat up the water. The pilot will light just fine, and heat up the thermocouple long enough to start the main burner if I quickly switch from "pilot" to "on". Sometimes the pilot will blow out for a second, and then relight itself, when the initial rush of air comes through when the main burner starts. Everything appears fine, then after approx. 30 seconds, the flame will shut down as if the water has reached it's temperature setpoint (which it hasn't) with an audible "click". I then can restart the whole process and get it to run for another 30 seconds. Here's what I've done so far in the last couple of days:

1) Replaced the gas valve for the water tank.

2) Replaced the pilot light/themocouple assembly.

3) Blown out the flame tube in the water heater.

4) Diconnected the gas supply at the water heater gas valve and checked for any obstructions. Opened valve at propane tank to let some gas flow through line.

Nothing helped, so I suspected that my gas pressure might be too low. So I lit all 4 burners on the stove, lit the oven burner and started the furnace all at the same time. The burners on the stove and the oven had good flames, and the furnace was putting out heat. Now I am back at square one

. I will try to verify that my lpg regulator has 11" WC. I will also try tightening up my thermocouple fitting (I installed it hand tight plus 1/4 turn per instructions). Has anyone had similar experiences? Please Help!

SteveH · 06-14-2009, 02:47 PM

I know you've changed the thermocouple, and it should be good, but if the pilot LIGHT goes out while the main burner is on, the thermocouple will cool, and shut off the main burner.

I believe your problem could be in either the pilot light intensity, or direction could also be a problem when the main burner is on. i.e. the draft from the main burner drawing the pilot light flame away from the thermocouple.

somefun · 06-14-2009, 03:13 PM

The pilot light and the main burner both go out at the same time (with a "click"). Pilot flame intensity could be an issue. I'm pretty sure the pilot flame is hitting the thermocouple correctly, and that the main burner is adjusted okay. Do these gas valves sense gas pressure and shut off if the gas pressure is too low?

SteveH · 06-14-2009, 03:15 PM

Quote:

Do these gas valves sense gas pressure and shut off if the gas pressure is too low?

Don't know for sure, but I don't think so.

If the thermocouple is getting too cool, it would shut off both the pilot and the main burner at the same time.

somefun · 06-14-2009, 03:36 PM

Good insights, Steve. When the main burner is going, the pilot looks a little lethargic

. Maybe the airflow created by the main flame is drawing it away from the thermocouple. But wouldn't the heat of the main flame be enough for the themocouple?

SteveH · 06-14-2009, 03:38 PM

Quote:

But wouldn't the heat of the main flame be enough for the themocouple?

No, all that heat is being drafted away to the flue and the water.

Excella CM · 06-14-2009, 04:29 PM

Maybe there is air in the heater instead of water?

Tinsel Loaf · 06-14-2009, 04:41 PM

Is there a way to put a piece of glass or a jar in front of the pilot to block some air flow and watch the pilot to see if the flame is being pulled away from the thermocouple?

somefun · 06-14-2009, 06:53 PM

I can watch the pilot as the main flame is burning. It's definately being drawn away from the thermocouple. And I'm wondering if the flame's too weak to overcome this draw. I could probably disconnect the whole pilot/thermocouple device, and hold it outside of the burner tube and try to fire it up and see how that goes. At least I could determine if the thermocouple is giving it the signal to shut off...

somefun · 06-15-2009, 09:23 AM

Ok, I finally got it to work. Here's what I did:

1) Checked gas pressure. Had 14" WC (minimum is 11" I believe)
2) Removed pilot assembly from burner tube and pilot stayed lit while main burner ran. So main burner was obviously pulling pilot away from thermocouple and shutting off gas.
3) Took pliers and bent pilot and thermocouple closer to each other, so pilot flame would engulf thermocouple. (just moved them about 1/4" closer to each other).
4) Reinstalled assembly into burner tube, further away from main burner to reduce pull on pilot.

Now it works fine. The pilot is further away from the burner draft, and is now closer to the thermocouple, which stays red hot from the pilot. Thanks for the help!!

Sixty3TW4US · 06-15-2009, 12:43 PM

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Eagle & Bear · 07-16-2009, 09:06 AM

I had a similar problem. Once the water was hot the pilot went out. Repalced regulator and WH burner and control. The WH pilot still would not stay lit. Blew out the gas line to the WH and found a well preserved moth that had been in the copper tubung. Problem solved but I now use a lot more gas.