My garbage disposal is jammed. And, using an allen wrench, I can turn the impellors only a 1/4 turn, at best. But, reaching down the drain, I can turn the impellors freely (360 degrees). And yet, the thing is still jammed to the point where the motor hums, but won’t spin freely.
What’s going on here?
Start by checking the reset switch on the unit somewhere. Also, are you saying you can turn the entire thing 360 degrees by hand, or you can turn the little chopper thingies (little metal pieces that move more or less freely).
The reset switch is fine. In fact, the motor wouldn’t hum if the breaker on the device had blown. The chopper thingys are the impellor. The impellores will turn freely by hand (360 dgrs) , but won’t turn by allen wrench nor by motor. Very puzzling… 
Jiggle it back and forth with the allen wrench. My wife ran a penny down the disposal once, and it took about 10 minutes of back and forth wiggling to get it to drop through.
The way to fix it is to put the end of a broom handle in (watch where the working end hits the walls or ceiling!) and try to spin the entire turntable in both directions. One way should free it.
In my case it’s usually from popcorn kernels, but the manual says onion skins, cellery strings, potato peels, pistacio shells, or even mashed potatoes or spaghetti left overnight to harden can jam it.
butler has a good suggestion. Here’s a quick how-it-works. The whole floor of the chamber (the turntable) rotates, connected to the motor. The little free swinging things swing out when the floor turns, and they force food out to the sharp slots in the sides.
You can turn the whole works will the Allen wrench from the bottom, but it it’s really jammed, a broom handle gives you more leverage.
Obviously, make sure it isn’t turned on before putting a broom handle or your hand in the chamber.
If the floor plate spins freely by hand from the top then it’s’ not jammed. It sounds like the motor has seized. If that’s the case a new disposal is in your future.
Disposals that have the Allen wrench port on the bottom/center to free jams are normally made by In-sink-erator but may have other brand names like Kenmore on them. Searching “In-Sink-erator” should give you troubleshooting, exploded views, and all that stuff if you want to be 100% positive before replacing it. But if I understand your description, it’s toast.
I believe that that allen wrench way of turning the disposal is pretty much of a universal thing. Not just Kenmore or Insinkerator.
A broom does get you a lot more leverage.
Believe the OP is a little confused about the thingys that turn inside, propelled by centrifugal force and not in any way connected to the motor.
Being able to turn those 360 degrees is meaningless.
It’s not.
The two main brands In-Sink-erator and Whirlaway have various rebadged models. The allen wrench port to un-jam the unit is specific to the In-sink-erator brands and will not be found on the Whirlaway brands.
The blades only swing out but don’t turn 360 but the grind plate does turn 360 and if it’s spinning free there is no jam to be “un-jammed”.
I cannot remember ever having a garbage disposal without that allen and the allen tool coming with it to turn the rotor in case of jamming. I have never seen a garbage disposal without that feature.
I have never owned an In Sinkerator. I don’t think that every garbage disposal I ever owned or any of my relatives, friends or neighbors owned was specifically a Kenmore or an In-Sink-erator.
Could be, but I doubt it.
They could have had pleny of other names but they were very likely* all manufactured my ISE. Names like Emerson, Kitchen Aid, Maytag, Whirlpool etc.
It may be hard to believe but trust me…
*I say very likely insted of simply “they were” because Im not considering the market outside the USA or models that are 40-50 year old antiques. I’m talking about the typical units in US homes now.
Detach the hose valve section from the bottom of the unit and see if there is anything clogging it up that is not visible from the drain.
It does sound like the disposer’s dead.
If you can look into the top end of the disposer and turn the large (it’s about 3-4 inches in diameter) plate freely, but you can’t turn the thing by using the allen wrench in the bottom, it’s sounding like the motor’s jammed or siezed, and the grinding turntable has come loose from the motor.
Happily, disposers are pretty cheap and easy to replace. I recently swapped an In-sink-erator with a Kenmore and all I had to change was the machine itself. The piece that’s mounted to the sink did not need changing, making the job that much faster. It truly took longer to remove all the stuff from under the sink and put it back, than the actual replacement.