It's fair to point out that the manual is very explicit in warning you NOT to change speeds unless planer is running. I knew that, but darn it, I don't like to make adjustments to running machinery. I'm the 'unplug, monkey with, then stand back, plug in, wait for sparks and flying metal, if none, stand further back and turn on, wait thirty seconds for blow up to occur, if none, cut' kind of guy. So with that mentality, I decided to switch speed just before starting to plain my QS white oak. Instant lockup on infeed. That said,
if you accidentally change the cutter speed when the planer is NOT operating, the infeed rollers refuse to operate. I called Delta, was on hold for twenty minutes, explained problem, waited another ten minutes while operator spoke with technician and was advised that the 'fix' is too complicated to be given over the phone and it must be returned to an authorized repair shop. Phooey. I fixed it myself.
You need to turn it off, lower the cutterhead completely down, let it 'bottom out' and then lift it up. Then, restart planer and ONLY WHEN PLANER IS RUNNING change the planer speed. It will eat up your material with its usual appetite.
As many have pointed out in the Amazon review comments, you can't tell the difference in dimensioning speed and finishing speed, so just leave the darned switch alone.
Jim