On Sun, Jul 4, 2010 at 8:13 AM, David Beierl <dbeierl@attglobal.net> wrote:
> At 05:11 AM 7/4/2010 Sunday, neil n wrote:

>>
>> Looking at my air cooled Haynes I see how the switches work in terms
>> of lighting up the brake lights, but am not overly clear about the 3rd
>> connection to the Brake Warning Light......

> Those are SPDT switches; the NC contacts are grounded through the brake
> lamps, and the blue/red wire from the warning circuit at track 76 is
> connected to both of them. �If both switches operate then the NC contacts
> float open and nothing happens. �But if one switch operates and the other
> doesn't, the blue/red wire sees the +12 going to the lamps, and starts
> hollering.

Neat. Ok. I get it. Thanks!

Originally thought that a ground needed to be connected to
semiconductor in brake warning light unit to light it up. But I
understand. If one switch fails, 12V gets sent back to semiconductor.
Didn't think to look at the bulbs as being conductors. Clever. As is
the oil pressure connection. (different purpose) Neat.

> If you want an instant brake light indicator just jumper the 81a (bl/r)
> terminal to the 81 (r/bk) on either switch. �Or for a stealth approach, turn
> on the overhead light -- you should be able to see it dim ever so slightly
> when the brake lights activate.

I assume you're referring to the retro install of a 2 contact
switch(s). I basically understand. I'll check my big green Bentley and
re read your comment on the jumper. Should be pretty obvious when I'm
"in there". (I'm the type that needs parts in hand or project in front
of him to understand things)

Heh. Stealth brake light. My interior lights are conveniently
connected to my aux battery. Besides; with the grounds all cleaned up,
the interior light is just too bright to have on while driving!   ;)

Neil.

-- 
Neil Nicholson '81 VanaJetta 2.0 "Jaco"

http://tubaneil.googlepages.com/

http://groups.google.com/group/vanagons-with-vw-inline-4-cylinder-gas-engines