My son and I both have Green Mountain smokers. The smokers are similar though mine is close to a decade newer than his and likely sees twice as many cooks a month. For the last year he has been fighting a sooting problem. Soot is coating his cooks and creating a real put-off in appearance and flavor. He has put the super duper deep clean on the smoker, made certain that the fans are all functioning as they were designed, changed to a more expensive pellet, and has resorted to filtering his pellets to insure he has no pellet dust in his burn pot. Nothing has improved the problem he is experiencing. I, on the other hand, have had zero problems with sooting, I'm quite guilty of letting my smoker get pretty dirty between cleaning, have likely never cleaned mine to the extent he has cleaned his, and have never concerned myself with pellet dust.
There are differences in how the two cookers smoke. My smoker has a hardened glaze of smoke and grease that can't be scrapped from the inside of the hood of the smoker. My chimney has to be vacuumed out every time I clean the smoker to remove the build up of tar buildup inside the chimney. I get the same barnacle buildup between the hood and the smoker body. He experiences none of the above with his smoker. We both have to vacuum the bottom of the cookers and burn pot to remove the ash buildup as well as changing the foil on the grease ramp. It is evident that they don't cook exactly the same. However, whatever is causing his soot problem is a more recent problem after years of stellar service. It is a mystery that we can't seem to figure out. It is a problem that has him considering tossing his faithful smoker for a new model.
I have googled the problem and there have been complaints and they point to the controller being the culprit. I'd buy into that but he had eight or nine years smoking before the problem started. I'm guessing it is some sort of air flow change which would be one of the fans not operating as it should. The fans are running but we have no idea the rpm and times they are to run. He could invest in a new controller but there is no guarantee that will fix the problem. He is leaning toward buying the cheap Pit Boss or something similar.
Any thoughts of something to check would be appreciated.