I know how convenient microwaves are so it can become frustrating when they stop working properly. I am happy to help. From the description you have provided, I suspect a relay on the control board is stuck in a closed position.
However, this will require a technician to check and repair. This is because microwaves contain high-voltage components that can retain a lethal electrical charge of up to 2200 VAC -- even when the microwave is unplugged. Repairs and adjustments, even minor ones such as , can cause microwave leakage. A microwave shielding leakage test should be performed after any microwave service. It is for these safety reasons that we are unable to guide you in microwave repairs and instead recommend scheduling service with a qualified service technician.
You can schedule for a service appointment via this link:
Sears Home Services
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