Amana Microwave won't cook

I have an Amana Microwave that is heavy duty , like I mean it has a metal chrome plated handle that pulls down from the top like a regular over. It has a stainless steel interior and has given good service. Now it turns on and sounds like it always has but it will not cook any food. I have a suspicion that there is a fan in the top of the oven that is not turning. I do not know if this is the problem of if the fan has its own motor of if there is a drive belt that is broken. I have not disassembled it. It really has not gotten much use in its life. Yet it is constructed so heavy duty like I hate to give it up. I do not see any microwave ovens built as sturdy as this one is.