Atwood gas/electric water heater not firing off

[BillHoughton]

Just filled with questions on our new RV. On our trial trip, four days away in a state park, we found that the water heater needed several attempts, each time, to fire off. It's an Atwood gas/electric heater, with electronic ignition, but we've used it in gas mode only so far (the campsite didn't have hookups).

I've cleaned out the burner tube here at home, and have run it (again on gas; the electric is coming, but it's a long story), and find that the igniter is clicking, and the flame catching, but it's not holding, not staying on.

Possibilities to explore, kind of in order of likelihood, seem like the thermocouple, high limit switch, and (failing all else) gas valve. But I'm not familiar with these heaters, previous experience being limited to pilot-type residential water heaters, and am sure open to advice and suggestions.

[ddro]

IF THIS IS A NEW UNIT THE PROBLEM SOUNDS LIKE THE BYPASS WATER VALVE IS CLOSED NOT ALLOWING WATER INTO THE WATER HEATER. We had the same problem our first time out. The unit was new and winterized so the valve was still closed. The water heater would fire up and run for about 20 seconds and shut off. Check the pressure valve and see if you are getting water out when lifting the valve. If not there's no water in your water heater. The reason it quits after 20 seconds is because the high temp switch is getting a hot reading telling it the water is hot but it's only the air in the tank that is hot. There should be a valve under the bathroom cabinet to allow water into the heater. I learned this by experience and was a little embarrassed but hey it's a learning experience LO
Hope this helps.

[enblethen]

The flame sensor is not seeing the flame. Make sure the tip of the sensor/ignitor is right in the blue flame.
You can use a long lighter to test the flame sensor. Light the lighter/ hold it directly under the flame sensor/ignitor to see if the flame holds. If it does the circuit board is good and the flame sensor needs to be adjusted. In some cases, the flame sensor/ignitor could have a crack in it and must be replaced.

[Dakota98]

On your next outing.

Light one burner on the stove top drawing gas into all lines. The HW should fire right up afterwards.