I have an AO Smith water heater from 2007. Recently, it wouldn't ignite, so I took the burner assembly out and found the fuse on the thermocouple was broken, so I replaced that component. All good for a little while, then it was out again.
I checked to make sure the thermocouple was fine (it was) and watched as the burner lit, ran, and then shut off along with the pilot light. I could re-light it but it would run for a shorter time, and then all go out at once again. Each time I re-lit it, it seems like it would run a shorter time. If I would get it running and then turn down the temperature, the burner would shut off and pilot light would stay lit.
I took the burner assembly out, vacuumed any dust from itself and inside the water heater and reinstalled it. The water heater will run for about a week if I do that, and then start having the same issues again.
I'm thinking of replacing either the burner assembly or the temperature/gas control valve. The flame is mostly blue but does get some orange flickers while it's burning. Any thoughts?