Some IS normal....it's just simply power draw. If it's to an extreme, then the bulletin explains the possiblity of a bad part.
The more electronics in a car the more it will pull from the electrical power system. Mine doesn't do it enough to annoy me, but I can tell when there's more draw. I've never owned a car that I couldn't.
In my house I can tell by the lights when one of the jacuzzis is turned on or the dishwasher is in certain cycles. Yet the oven doesn't. It's on a completely separate wiring system.
In a car, the A/C & defrogger are using the same circuts. Both use a lot of power, plus the car's computer is set up to change the idle accordingly. Since mine is garaged to sleep, I've almost never used the rear window defroster. They use a bunch of power & in past cars was the easiest to see the draw in the lights.
What can you so? First make sure (as suggested) that there's nothing weak on the car. Good output from the system. If that's fine, then have the part on the bulletin checked for flaws. If all that's fine, I don't know what would make a difference.
