Living in Canada last Sunday was the first time since owning the grill we haven't had a cool breeze to blame for fluctuations. Out of the four bags of various brands of pellets two brands are the larger pellets and those are the ones I was using on the weekend. I set the temp for 225 and over an hour and a half it would hold the temp for five minutes and drop to 165-180 for 20 minutes. this kept repeating over and over. I'll stick to the Weber pellets. Yesterday I read somebody removed the finger guard from their hopper I may look into that option as well.I tried B&B pellets (which are a larger diameter) and that was the only time I've experienced temperature fluctuations. I think the SF just struggled to feed the larger diameter pellets which caused the problem. I have since stuck with weber or lumberjack and have had no issues. I highly recommend lumberjack, half the price of weber and they work great!
you've replaced 3 controllers?? jeez, it must be that you have a dead short or something like that, somewhere else in your grill. I hope they get you fixed up, I love mineMorning, don't go crazy with the pellet issue. I have been using Weber pellets religiously for the last 2 months and since software 4008 this grill has a mind of it's own. I am on my 3rd controller, with the welded chute and I wish I could go back to 4003. I have been in constant contact with Weber and they are working on it... Plus my new wrinkle is the controller locks up and will not respond unless you power down the grill. The app (which is worthless) still thinks the grill is running perfectly. If you do not have a secondary temp monitor, I would get one, that is the only way I knew the grill screwed up without constantly staring at it for the 6hr cook. When it works it puts out great food, but don't turn your back on it cause it will bite you when you least expect it.
The first pic was after the controller locked up
The 2nd is went it restarted and it was set for 240 the controller read 270 but it was actually 361
Talk about temp swings, this is crazy