Loren, the important difference isn't for version B - M swaps, but for
version T swaps. According to VW parts data the version T headlight
switch is for certain of the last Vanagons made but the exact serial
number when it was introduced is given very differently in different
places in the same VW documentation. To see if your dash harness needs
the later T version switch you would have to look at the wiring going to
the switch. According to the Bentley diagrams the later T version wiring
has a wire to pin 58e while the majority of Vanagons have no pin 58e
with a wire to it. My early 90 Syncro has the older wiring to the switch
and no pin 58e. (my 90 vin# L 28,xxx)

There are still other letter versions of the switch not mentioned yet.

Neil was really looking to know if the version M replacement for version
B was a stronger improved one and that I can't answer.

My post was to warn people who might be tempted to use the cheaper,
easier to find early versions of the switch in their later wiring that
they would be bypassing important fuse protection if they did so.

My best guess is that the headlight switch wiring was changed to allow
DRL system flexibility. Since DRL was a Canadian thing at that point in
time the switch/wiring change may depend in part on which market the
particular Vanagon was intended for.

Mark

Loren Busch wrote:
>   RE: Headlight Switch Later Models
> Okay Mark, got that.  Now a follow on question.  Since it appears that a
> '90  Vanagon could have either the B or M suffix switches originally (and
> corresponding wiring) but either will appear to work correctly (but no fuse
> in dash light circuit if B used where M should be) then how does an owner
> of a '90 Vanagon check to see which is correct?  This assumes that a PO may
> have put in a B where an M was originally.  How can you tell which is the
> correct switch?
> BTW I'm asking because I think I may have done exactly that some years
> back, put in a B when an M failed.
>