Look things over one last time and then reinstall the upper burr.

Install the hopper WITHOUT COFFEE.

Plug it in and run the (empty) grinder briefly to make sure it all sounds OK. Try both coarse and fine grind settings. If it sounds wrong, investigate or comment below.

If all is well, add some coffee to the hopper. Dial in the grind and try it out!

Tip: There is a bit of a break-in period the first week where the new impeller builds up a protective coffee coating. I recommended using a medium to light roast during this period.