Austin didn't mention whether he has adjustable armrests or not, but the
procedure is basically the same.

1. Remove the armrest. (This is more difficult on the adjustable armrests
which require taping out a 1/4" steel plug.)  Even on the adjustable
armrest, there is no need to harm the upholstery, just push it out of the
way to gain access to the steel plug.

2. You are now looking at the bracket that holds the armrest to the frame.
Tighten/replace both bolts that hold the armrest bracket to the seat frame.
The looseness here is why the armrest will not catch on the internal stop
that holds it at a horizontal position.  If your bolts are stripped, you can
get a replacement at your hardware store.  Remember that you need a metric
size, but you don't have to be too fussy about the length, a bit longer than
the original is no problem.

3. Put everything back together.  If you had any other problem, it would be
obvious as soon as you tried the above remedy.  Solutions for broken or bent
parts need to be figured out on an individual basis.

It really isn't very difficult; take it from one who has done it a few times
on various vans.

Good luck.

Budd Premack
86 Syncro, 84 GL, 73 Super
Minneapolis, MN (Land of Frozen Waters)