When i open the door only the light is supposed to come on. the light comes on but the fan and turntable run also.

Use some good old Duct tape on the spindle. :-)

Brand new, take it back where you got it from then, no point fiddling about endangering your guarantee.

The motor is most likely open circuit. Solutions are going to be either replace the motor OR if the thermal fuse on the windings is blown you will need to get one of the same value and replace it. The value is written on the fuse and it is under some fibreglass tape on the field winding with the aluminium clip around it. You need to remove the motor completely to do it.

You might have figured it out, but the problem is that you haven't locked the jar properly. Be sure that everything es lined up, and that you have turned the jar and locked it with the machine. If you do this, you will be able to turn the button from 0 to I even if there is no power.

Remove and check if there is any fault of a brush contact or switch contact or if the load trip switch had reset.
If the power is coming to the motor and is not running you need to confirm fully if the windings are open , if so replace motor.
if not remove and reset the setting of the brush/commutator.

Yes, it should. Most will take a few hours (two or more) to cool down to a "safe" temperature so you can open the door. If it has been more than 12 hours, you may have a door lock issue and may need to schedule a service call.

Ineed a TYJ50-8A19 motor for my Cuisinart microwave where cn I find one

Not positive as to your problem, but I was just given one of these and thought it didn't work. On closer inspection, I found a little switch that needs to be depressed from the bottom side. When I pressed it with a tiny screwdriver while holding down the bar on top, the motor runs!

I just have the white top with the motor and the glass jar thing. So I'm on a search for whatever is supposed to fit between them. There's room for a seal between the two, and I imagine it has something to push the tiny button, to activate the motor (guess technically it's a safety interlock).

In case it isn't obvious where that button is, turn the motorized plastic top upside down and look at the center. There's the star drive in the middle, and four little depressions, or holes around it. One of them isn't white inside. It's the magic switch! When I push it with a screwdriver and push the power bar, the thing comes to life...

If that works it for you, then your new mission is to figure out what pushes that button and put it in the right place.

I started from scratch with the assembly instructions. Got it together correctly and now everything works.

Try adjusting the speed up or add the onions a little at a time. Another sugestion would be to use the blade holder and run the onions thru that way ( Shredding them) prior to doing the rest of the reciept with the quad blade.