To further clarify on Mark's comments (they were all right as far as I
know), the coolant temp. sensor II, or the one to the brain, on the plug
part is a nice pretty blue--new that is, at least on an 87.  The one
sitting in your engine compartment is also blue--once you get all the
road grime off of it.  If your mechanic has trouble finding it in his
cross-reference book, it's because it's listed funny.  I can't remember
where my guy finally found it, but it wasn't listed where he thought it
should have been.

Tonya
87 Vanagon GL Wolfs
74 S. Beetle