Nucamper here! (get it?)
Thank you all so much for the great info you share here. I've been able to get a number of questions answered and solve some problems with our 2020 400!
One issue haven't been able to solve: My Alde pump sounds a bit like a garbage disposal choking on it's own fluid.
Our family was out at Great Sand Dunes National Park last week, and overnight the heater was so loud that I had to shut it off so we could sleep. Thanks to this forum, I was able to determine that part of the problem was that the appropriate high altitude setting wasn't enabled, so I took care of that and tested again where we live in Monument Colorado (about 7100ft), and it fixed part of the problem, but now I am having trouble with the pump noise. Thanks again to info on this forum, I was able to locate the pump itself and make sure the speed was appropriately set, which it was, at about 1.5 setting.
The best way to describe the sound we're hearing is that it sounds like the pump spools up and then gets bogged down - almost like constantly fluctuating RPMs. Imagine turning the garbage disposal on, then dumping some things down it that slow it down, then it spools back up again, if that makes sense. Fluid levels look ok when I check the tank in the wardrobe. Got some good bouncing around on Colorado BLM roads that I think would've "burped" the system.
At any rate, I'm pretty confident after reading a number of other member's descriptions that it's not running correctly.