Your microwave cooks properly, but it doesn't turn your food around on the internal carousel. Several potential problems may cause this scenario. If you have access to the manual for your specific microwave model, the troubleshooting guide may address issues specifically related to your model. In most cases, though, one of several chief issues causes microwave turntables to stop spinning.
Clean and Realign
Your microwave turntable may not turn because of a simple mechanical problem: It may have become caked with grime and is sticking, or it has simply slipped off its guide. To cover both scenarios, remove and wash the glass element of the turntable, removing any food particles or debris. Do the same for the guide, the piece that rests below the glass plate and transfers the circular movement from the turntable motor up to the plate. Remove any grime from the delicate rollers at the end of each of the guide's spindles. After thoroughly cleaning and drying all elements, carefully return the parts to their proper positions. Set the turntable guide into place, listening for any clicks that may signify a good fit. After you have gently but firmly put everything into place, test the microwave to see whether the turntable spins.
If cleaning and realigning the turntable elements don't fix your problem, your turntable motor is likely broken. Disconnect one of the motor's wires, and use an ohmmeter or continuity tester to check whether it carries a charge. If not, you can usually find replacement motor parts for major brand microwaves. If the motor, itself seems to be working fine, inspect the wiring around it; if there is damage there, replacing the motor itself won't remedy the situation.
Loose or Broken Belts
If your microwave has a belt-like connection between the motor and the turntable housing, the microwave may have an excessively loose or broken belt. If you detect that the belt has broken, you'll need to replace it. If the belt is intact, see that it's also quite malleable, stretching by about 25 percent. If it stretches too far or not far enough, the element may be worn out or excessively dried up. Also, after stretching, the belt needs to return to its original length.