Atwood water heater won't stay on.

After it runs for a while and goes out, does it reignite by itself or do you reset the switch? Flame rectification is touchy and everything in the circuit has to be kept really clean. The ignition module gets a micro amp signal, through the ignitor, when the flame is present. The flame actually is part of the circuit and conducts the signal. The igniter rod and porcelain insulator needs to be clean. Wipe off the igniter rod insulator with a CLEAN cloth and alcohol and check it very very closely for any carbon tracking. Clean the igniter rod tip with Scotch-Brite pad or really fine sand cloth. Replace the igniter rod, if in doubt. They are cheap. Primary air adjustment is important and that’s why the flame should not be roaring or lifting because of too much air. If the flame lifts off the burner Or loses contact with the flame rod, the rectification circuit is broken and the gas valve will shut down immediately. Even the ratio of flame contact area between the burner and the flame rod is important. Make sure the end of the burner where the flame contacts it, is also corrosion free. The ground path from the burner to the module is also part of the rectification circuit so I added a copper ground wire between the burner and the module ground point and I used Deox on all the rectification circuit connections.
That covers almost all of the rectification issues and if you do all of these things, you shouldn’t have a problem with the flame rectification signal. Craig