AO Smith heater won’t start

[Usmc93]

I have a gas AO smith water heater. It was showing 3 lights yesterday (Vacation, A, and B) would turn on, glow, try to ignite, fan on, and then turn off after a few cycles of that.

I took the pilot light out and sanded and cleaned the flame sensor and it fired right up when I put it back in. The hot water heater ran and I was able to take a hot shower but then 2 hours later it was off completely and even when I unplug it and plug it back in nothing happens, no fan, no ignite, nothing.

I have no error codes and when I hold the hot and cold button two lights (A, B) light up as if it’s working.

I have no idea how to fix it. The other question I have, you can see the clip in the far left corner of the pic. There’s a metal clip with 2 wires going to it and two pink caps on top...a white roundish thing underneath. After putting it back together I just clipped it on the outside where it is now but I wasn’t sure if it belongs inside with the pilot.

note, this pic is after I got it to run again but before it shut off.

 

[breplum]

Make sure supply air inlet zone is completely clean. Often located in completely inaccessable narrow space that you need skinny long brush for.
You said fan...so can't tell what you have without pics.
general suggestion for update here: model number and pic of the control and added to this post
Look up troublshooting in the manual then, if necessary,
call AO Smith to get help
May need millivolt meter to diagnose.