Joe,
First why are you replacing the thermo? If it's not defective keep this one????

If defective you should be running cold!!!! (stuck open)

If you really want to replace this one put the OEM one, take this one at VW,
the company that built your van!!!!!!
They were at the letter 000 000 000 "F" last time i bought one.

You should also double check this new one in boiling water.
The 87 is OEM, not the 80.

Replacing the switch is call preventive maintenance (if it's old), it is
only a high end safety, not much to do with the thermostat. If the front rad
become to hot(at around 1/2 to 3/4) it should start the fan.

This occur when the 87 or 80 is fully open and the air circulation is absent
(stuck in traffic), in other worlds, even if you have a 80 and no air in the
front the temp will rise until the themo kick in, this one should kick in
just above the 1/2 mark, if it kick in over 3/4 change this one.

Running to cold is not good either (fuel consumption), normal driving
condition should be with the temp needle at 1/2 mark.

http://www3.sympatico.ca/huotx/front_radiator.htm
http://pages.infinit.net/engine/cooling_system_flow.htm

If your running hot, check other stuff!
At the same time you should change the blue temp sender:
http://www3.sympatico.ca/huotx/temp_sender.htm

Cheers, Ben
http://www3.sympatico.ca/huotx/engine1.htm

---------------------------------clip-----------------------------------
A few quick questions. I'm replacing the thermostat; should i get the 80
degree or 87 degree. Is it necesarry to change the Cooling Fan Switch to
correspond with 80 or 87? Where can I find an easy to read diagram of wires/
sensors in the Vanagon, especially near the bottom of the engine. There are
a few mangled, but I don't know what is what to replace. Thanks for reading.

Joe Lucca