Our microwave turntable is making a grinding noise when in use. When we turn off the turntable the microwave is quiet, but food is not heated as well, due to the turntable being off. Any ideas about what could be causing this and how to fix it?

The very first thing to check is that the turntable is clean. Crumbs under the wheels of the turntable can make a nasty grinding sound. Inspect the wheels too, make sure nothing is stuck on them.

IF everything is clean, then the drive mechanism is the likely cause. It could be a plastic gear is worn, cracked or misaligned. It could be dirty. The motor may be failing.

The thing to understand is that the microwave is extremely dangerous to service yourself. Do Not Open the housing, there is a capacitor with a charge of several thousand volts inside.

Unless it can be serviced from the outside, our general recommendation is to simply replace a microwave rather than repair it. For example, my own mic needed a new handle, the part was $118. I replaced the whole microwave with a better one for $10 more.