Your microwave oven not working?
I am sure tht many answers blame magnetron is faulty. Why, because is expensive and not worthit to fix. I fixed nearly 200 microwave ovens ( customers returns from shops) and only about 4 magnetrons need replacement, usualy in branded models. High voltage transformer is rare to get faulty ( about 2 out 200 ). Will smell burning smoke from apliance, it is from high voltage transformer.
First thing, microwave oven is very danger apliance to repair due high voltage. If you do not know how to deal with electric items ask specialist. On my blog will find instructions [http://bargains-zone.co.uk/en/blog/all-post.html|how to fix microwave oven.]
The most common fault and very cheap to fix is [http://bargains-zone.co.uk/en/small-electrical-spares/120-high-voltage-microwave-oven-fuse-08a-5-kv.html|microwave oven high voltage fuse]. This part is attached to tranformer in black or white plastick tube. Need carefully open this tube using flat screw driver. Will see glass fuse, clearly will show you if is ok or need replacement. If you replace this plart, before try apliance if working is got to check high voltage diode and capacitor. If one of this parts faulty, your new fuse will burn again in seconds.
Door switches are for safety, have nothing to do with warming food.