The possibility exists that you may - emphasis on may - have a clogged
radiator.  Have you felt the radiator at different areas?  If it's clogged,
there's going to be warm (hot) spots and cooler spots.  If you pulled the
fan switch, shorted it out, and the fans kicked in, maybe there's a clog
somewhere near the sensor that's not allowing hot coolant to pass by the
switch.  I would start the van, let it run till warm and feel around the
radiator for hot/cold variation.  You may have to pull the radiator and
have it blasted out, or replace it entirely.

Alan Bosch
Phred ('88 Wolfsburg)

PS  One thing I found a few weeks ago, when doing a coolant flush and
replace:  The DPO (or the shop they hired) had replaced the thermostat
upside down.  When I put the new stat in - the right way - Phred startd to
run cooler.