Garbage disposals aren’t hard to fix if they aren’t worn out. Most problems come from either a wiring problem, or something is stuck in the mechanism. You have to first pay attention to what your disposal is doing. Is it just not doing anything when you flip the switch? Is it humming or buzzing? Does it run, but you hear terrible noises inside of it?
If it’s not doing anything when you flip the switch, the problem is either in the electric, or the motor is shot. But before you get too carried away, climb under the sink and look at the bottom of the unit. There is a small red button on most disposals. This is a reset switch. If something put the motor into a bind, it will shut the unit off to keep from burning up the motor. Push the button in. If it clicks or stays in, then probably that is the first problem to be fixed. Flip the switch on the unit. If it buzzes or hums or starts running, you have fixed the electrical problem. Turn it off before proceeding. If nothing happened, check the breaker box to make sure that a breaker isn’t thrown before doing anything else.
If it was running and sounding normal, you are finished. If it made loud noises, you will need to shut of the power. I recommend shutting off the breaker. This way if you accidentally flip the switch, you won’t loose body parts in the disposal. Reach inside the disposal and feel around. If you think this is gross, use a glove. You should feel the fork or spoon or toy that is inside. Remove this and your disposal should work properly.
If you had the buzz or hum, then you may have something stuck in the grinding part of the unit. You should have received a large hexagonal wrench with the unit or have one in a drawer. If you don’t, climb back under the sink and in the middle of the unit you will notice a hexagonal hole. You will need a wrench of the correct size to fit it. Once you have the wrench in hand, and the power is off, use the wrench to work the grinding unit back and forth until it turns easily. Turn on the power. If your unit works correctly, you’re finished.
If it still buzzes or hums, you probably need a plumber or more likely, a new garbage disposal.
If you disposal just sits quietly and does nothing, it’s time to check the wiring. Turn off the power. If you’re electrically inclined, climb under the sink with a screw driver and remove the panel from the disposal where the wires enter the unit.
Turn the power back on to the unit and turn on the switch. Using a multimeter, test the voltage coming into the unit. If it registers as the proper voltage of about 110-120 volts, you need a new disposal. If you have no power, you have a wiring problem. If you are electrically inclined, track down the loose wire or bad switch and fix it. If you are unsure about this, call in an electrician.