1990 Aerostar 4.0 FI 350000 km
Does anybody have any ideas about how to open it, I locked keys in there?

 

I have never tried this myself, but a long time ago, I read of a flaw in the locking mechanism in the sliding door of the Aerostar. With the door locked, if you pull on the handle, it will open a gap. Through the gap, part of the lock or latch mechanism is accessible with a rod of the right shape. With the right fiddling, the door can be opened, while the lock is still applied.

The person who told me this happens to be selling a gizmo that's supposed to prevent this. Again, I've never tried this, so I can't verify it.

 

It did not work.

 

Use a coat hanger to open the window on the slider, you can then reach in and open it up!

 

oops I broke the window

 

Done this mant times. . Be careful when sliding the coat hanger from the rear over lap. Put a small hook on the end. slide it all the way to the front and use the hook to pull the latch. Sometimes it helps to move the window a llittle to take pressure off the latch.