down home wrote:
Spiders and other critters like the tube.
Clean every season as per manual. Soot build up of itself and oxidation of the metal may be a problem. All those parts are available pretty cheap.
I second this. I just replaced circuit board and ECO as my water heater wasn't working and poof it ignited. Luckily I went out to check the flame, as it'd been a couple months, and found yellow flame coming out of intake flue and exhaust nearly burned up my RV. Quickly turned off water heater and went back to basics trying to adjust flame and still no improvement. When I ran a pipe cleaner through the burner tube and flue, out came a spider and web. A little shop vac cleaning and it works perfect now.