I realize that I'm coming in the middle of this disciussion but I could
not hold myself back.  I've been fixing VW vans since 1970, for about 28
of those years people have paid me to do it & I went to many of the VW
service schools in the '70's.  I've been around & around with the parts
quality issue & here is another thing to think about.  Most car makers (VW
included) do not make all their own parts.  They buy them from "vendors".
The maker (hereafter referred to as VW) designs the van & figures out what
they need to make it work, in this case a coolant level warning
light "relay".  VW figures out what the "relay" is supposed to do &
contacts electronics makers to have it built.  When the "relays" are made
they get some sort of testing to see if they will work as originally
intended.  Then they are installed on the vans.  Now comes a crucial
point, suppose that after a while that many vans are returning to the
dealers with always blinking coolant warning lights.  Eventually the
problem is traced to the "relay" & a new design is created.  The
new "relays" fix the problem, but what happens to all the "old" ones on
the shelves at parts depts. & warehouses?  Ideally they would
be "recycled" & not used, but what if they get wholesaled out the back
door? After all some of them worked some of the time.  So that less
expensive part you might have bought could be less than ideal in function
even if it has an OEM logo & part # on it!