Atwood water heated will not stay running.

[Breed1229]

I’m hoping someone can help me out. I have an Atwood G6A-8E that will not stay running. I can turn it on when it’s cold and it will run for about 10 minutes. I have timed this. Occasionally it’s a but longer or a bit shorter, but about 10 minutes. Then it turns off and I get the fault light. If I turn it back on it will light and run for 5 seconds. Then if I let it cool it will start this all over. 10 minutes and then 5 seconds.
I have replaced the thermostat , the ECO, the igniter, the circuit board and I’m waiting on the valve body. Same thing.
I’ve cleaned all the connections and grounds. I’ve verified that the U tube is clear and that I have over 12 volts to the board and that the he bypass valve is in the proper position. Maybe the valve is broken? When it lights it runs nice and blue with just a slight roar.
Tonight I’m going to blow out the propane line to the heater just to be sure. I’m not really thinking that there will be an obstruction but what do I have to loose.
What am I missing? I’m sure it’s somthing silly. Racing season is here and I really would like a hot shower after a sticky day at the track.
Thank you in advance.

[BFL13]

Perhaps the "thermal cut-off device"? (on the incoming power wire and is connected to the thermostat) If there is an obstruction in the burner or flue tube (mud wasps, eg) it will trip. Also the exhaust grill on the access door must be clear or it can trip the thermal cut-off. The wide band on the grill must be at the bottom. If at the top, pop it out and put it in right way up.

[Old_Days]

I am not a RV tech but it does sound like a bad thermocouple.

[midnightsadie]

don,t no much about them ,but it has a thermocoupler on it it could be going bad.