84 uses a different switch than the 85. In fact there is a 3 wire switch
for 80-84 and a 2 wire for 85-91.  The earlier type incorporates a brake
pressure failure warning circuit and that is why the 3rd wire is needed.
The switch design change for 85 and newer may have been made in part to
allow for a more sensitive brake light function than the earlier brake
pressure system failure detection feature allowed. The 85 and newer has
a fluid level float switch in the fluid tank cap instead of the pressure
detection.

Mark

Mike Collum wrote:

> I just came in from driving my '85 Westy (It's dark in Maine already)
> which has a 3rd brake light that reflects enough on the hatch for me to
> know when the brake lights go on.  On that one, the lights come on prior
> to actually applying enough pressure to say that braking has started.
> In other words, I'm happy with the way it works.
>
> My '84 7 passenger, however, is another story.  Its brake lights don't
> go on until braking has started.  I have a set of new switches for it
> ... I just haven't put them on yet.
>
> Mike
> Houlton, Maine
>
>
>
> Jeff Oxroad wrote:
>
>> In summation, in my opinion the pressure needed to illuminate the brake
>> lights should be lower. Does anyone else suffer from this gremlin, or
>> is it just my
>> bus?
>
>