According to GE as well as experts in appliance repair, a repair technician should be called if a microwave is running but is not producing any heat. The problem is likely related to the microwave's circuitry, which is very intricate, and attempting to repair it without expert knowledge is dangerous.
GE declines to provide any do-it-yourself advice on this issue due to the extreme danger. GE also notes the specific equipment needed for troubleshooting and diagnosing microwave issues, and cautions that there is high potential for incurring electric shock due to high voltages. The website does provide a customer care line to call, as well as the option of scheduling a repair appointment online. If the microwave is still under warranty, the terms of the warranty should be reviewed prior to scheduling an outside repair technician to do the work. If an extended warranty or care plan was purchased from the retailer at the time the appliance was purchased, that agreement should be checked as well. Repairs that are not covered under the basic warranty may be covered by the extended warranty. If the microwave is inexpensive or an older model, replacing it may be a more cost-effective option than having a repair technician examine it.