Any suggestions when the disposal won't drain and you've already tried to plunge it?(didn't work) It's a dual sink and the non-disposal side drains properly, so I'm not sure the drain trap is the problem. If I dismantle the drain trap and discover it is not the problem, what next? Thanks in advance for any advice

There is a blockage somewhere in the pipe. Either where it is connected to the Disposal or in between there and where it connects to the drain lin from the other side of the sink. Since I do not know what your systen looks like I will just give you a general discription of how it might look. You may have a p-trap connected to the disposal and another p-trap connected to the drain from the other side of the sink both of these connect to a Y fitting before it goes into the wall. If this is the case, loosen the U shapped bennd below the disposal, and tour the water out of it. You may find the blockage in it. If not stick something into the drain going to the Y connection and see it you unstop it. If not, go up toward the disposal and see if something is there. If none of these work there is a L shapped piece connected to the disposal remove it and see if you find anythang in the disposal itself. Good Ludk.

You might also make sure there isn't anything in the disposer. Usually, the way disposers fail, the swivel impellers on the grind plate get so corroded, they can't move. The motor runs, but the impellers don't move and grind up whatever is in it. Sometimes we take for granted that it's grinding because it's running, but that may not be the case. You can use a long screwdriver to insert through the splash guard down to the impellers (usually two of them) and see if they rotate. They should rotate easily. If they don't, and the holes around the edge of the grind plate are plugged with food debris, it's time to replace the disposer, since they usually can't be repaired (and probably not worth it if you could).