This article is from the Chrysler-Plymouth-Dodge FAQ, by Dr. David Zatz with numerous contributions by others.
(e-mail address removed): on a 1987 Caravan, the gas gauge kept creeping up
to full. The problem was a small circuit board, part 4375318. Dean Seaman
added the board is no longer used, but did dampen pointer movement. Some
gauges used a thick liquid instead.