My microwave does not heat but there is power

Sounds like the magnetron has failed. This is the component that produces the microwave that heats the food. The cost of the magnetron is about 95% of the cost of a microwave . Most people don't, for this reason, replace the magnetron, they replace the whole oven which is probably what you will end up doing. There is a possibility that the circuit that provides power to the magnetron is faulty and you need to take it apart, find the proper electrical leads and test them with a volt meter. To do this you have to remove it from its mounting and take it apart. It is a fairly lengthy process however.

Benjamin