Why won't my interior microwave light turn off and my microwave won't start?

Take it back for a replacement. You have a bad door switch and it is not recognizing when the door is closed.

Semper Fi,
Z

Need a bit more information here. Does it still cook when told to do so? If not, you may have a problem with the door close switch. Perhaps it is as simple as using a screwdriver to finesce the actuator back into position. The inside edge of the door has a metal latch and often times a slightly shorter pin or tab that actuates the door open switch. This not only enables the light in the microwave to turn on when the door is open it also tells the cooking circuits to disable until the door is properly closed. If the switch itself is bad you'll have to take the microwave apart to get it out. RepairClinic.com has a huge assortment of parts that are easy to search and find.

You probably have a shorted cook relay.

We regularly repair this problem with our $39.95 service, or you can order a new circuit board from the Pros here, our favorite supplier.

see this causes and fix it. God bless you
Open Lever If the microwave door won't open the open lever might be broken. This part can be replaced separately.

Door Spring If the microwave door won't open the door spring may have broken. The door spring is located inside the door and keeps downward pressure on the door hook.

Door Latch If the microwave door won't open the door latch might be broken. The door latch is inside the microwave. The door hook, which is part of the door, engages with the latch to keep the door closed during operation. If the door latch or actuator breaks the door may not open.

Door Hook If the microwave door won't open the door hook might not be releasing properly. The door hook is installed inside the door and normally releases when the door is opened. The hook is made of plastic and will break over time. When this happens it will need to be replaced, it can't be repaired.

Button Spring If the microwave door won't open the button spring might be broken internally. The button spring can be replaced.
Button If the microwave door won't open the button might be broken internally. The button can be replaced.

Handle Actuator If the microwave door won't open the handle actuator might be broken. This is a plastic part which can become brittle over time. This part is connected between the door button and the door latch assembly.

I have the same problem. Is the light still on inside the microwave? Mine is on and the microwave thinks the door is not shut. I took the top off of the microwave and the latch needs to push down on a switch once shut. The latch was reaching the switch, but I think some spring in the door, pushing the latches down, has broken since it reaches the switch when closed but there isn't any downward force to flip the switch.
I am trying to figure out how to repair the latch but if your light is on when you "shut" the door, you may have the same problem.

One or two of the door switches has failed, replacement only option, consider price.

I had this exact same problem with my salton microwave! Even tried taking it back to the store, but with no reciept there was little they could do. Anyways try jiggling the clasps on the side of the the door, the ones that connect it to the microwave. Mind you don't jiggle too hard. Now firmly close the door, you should hear a distinct click. Now try it! The light only works when the microwave is on. The microwave won't work unless the door is closed properly and my problem was the claps were stuck! I hope this helps.

If the microwave oven operates with the door open it is a serious issue. DO NOT OPERATE IT. Call a technician immediately. The RF frequency is extremely dangerous. the safety switches inside the oven are malfunctioning and needs to be replaced

It is possible that the magnatron is bad but hard to say on a no heat problem without checking all components. A lot of model give 5-7 yr warranty on that part.

If you're saying that the inside light won't come on when you opoen the door, then you probably have a bad door switch, most likely the upper one. The most common causes are opening the door while it's cooking instead of hitting the STOP pad first, broken switch mounts, and damage to or slamming the door. These switches are locally available at appliance parts companies. I have a helpful text file with critical safety information and info on diagnosing and replacing door switches. You can find it by doing a search on Yahoo.com (not Google) for microwave doorsw.txt I appreciate your rating of this answer.