WHAT CAUSES FUSE TO BLOW WHEN DOOR OPENS. I CHANGED IT AND SAME THING HAPPENS OVER AND OVER.

I would change the interlock switch under the door catch. They do intermittant things like this when contaminated.

need a meter to test motor and circuits-if motor seized or shorted will blow fuse

That would be a problem with a door switch, door switch mount, or hinge.

See my help file on door switches here:
http://www.microwavecontrol.com/doorsw.txt

There are several switches (usually 3) located and attached to the door latch area of the microwave. One is a safety interlock that keeps the Micro from running with the door open. At first one of the switches were sticking slightly giving you the attempted run. Then enough stuck to cause the safety to sense it. The safety usually will blow the internal fuse or house breaker. If you are going to get it fixed, best to replace all the door switches and then the fuse also. If by chance it still blows the fuse again you have other problems. At this point I think its just the door switches and fuse.

If you're blowing fuses from opening the door that is the sign of a electrical short . You'll need to call a electrician to check it out. Changing the fuse in this unit can kill you. There's a capacitor that holds stored electrical energy that is dangerous. My good friend died from trying to change the fuse in his. Get a professional to check it.

Having 20 year experience fixing microwaves i know that when the fuse goes that if you can't find a melted wire or overheated components on the circuit board that the high voltage capacitor at the back needs to be replaced. Sometimes you have to replace the magnetron too. You can replace the door switches if you like, microswitches are inexpensive but would only be bad if arced inside so bad that you read over 1 ohm.

(Fuse is a ceramic fast blow 20A Little Fuse 0314020 or Eton ABC-20) Melting I²t 631
If the Fuse blows when the door is opened. (not even energizing the microwave) The bottom micro switch (monitor micro switch) is normally closed, (open when the door is closed) however if it remains in the closed state when the door is open you will have a short circuit with the Primary Micro switch. The circuit diagram shows that one of the two switches must be open. I was able to test with an ohm meter. With a bad switch the reading was less than an ohm with the door open and 290 ohms with the door closed - Across the plug with a good fuse. With the new micro switch the resistance shouldn't change by much with the door open or closed.

It's possible the high-voltage capacitor is bad, but I suspect a bad interlock monitor switch. This is one of several switches operated by the door latches, and it's wired to cause the fuse to blow if you try to operate the oven with the door open. The switch may be stuck, which can happen if the oven door gets slammed. It's also possible the switch is good but is out of adjustment.

Replacement switches are available. The Sears parts website has an exploded diagram showing where it's located (item number 30). You should let a professional make the repair, though. Microwave ovens are dangerous items to work on, and if door repairs aren't done correctly there can be excessive microwave leakage.

The Interlock Monitor Switch is an added
safety check on the Primary and
Secondary Interlock Switches. If the
Primary and Secondary Interlock Switches
allow the oven to operate with the door
open, the Monitor Switch will blow the
fuse.

You can get more information about adjuting the interlock switch from this link

http://136.166.4.200/contents/Microwave/LMVM1935xx/LMVM1935xx_Service_Manual.pdf

sections 7-11 thru 7-12 discuss the door interlock adjustment that will cause the 20A fuse to blow if it isn't set up right. I hope this helps you...

You are decribing a typical Door Safety Switch problem. The Door Safety Switches has Failed.The Door Safety Switch is designed to shut down the Micro in the event the Micro is still cooking when the door is being opened. The first "Click" of the switch cuts off the "Cook". If it does not cut off the "Cook", the second "Click" blows the power. Otherwise it would "Cook" with the door open, and I need not to tell you how DANGEROUS that could be. It first Tripped the Circuit Breaker which supplies power to the Microwave. After Re-Setting the Breaker the same thing happened except this time the Micro is DEAD- not even a light working. Yes, there is a line FUSE inside the Micro. You however need to address the Door Switch SHORT before replacing the fuse. If not, it will just Blow The Fuse Again, and Again, until the Short is corrected.
Call around, ask How much to replace a Door Safety Switch.
Good Luck!