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. Is there something in the
>switch(s) that activates causing light to go on in the event of a
>hydraulic pressure loss? Haynes says if light stays on, (all else
>correct) then a fault lies in the hydraulics. I'll search that one.
>I'm sure it's in the archives.

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.

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.

In '85, if you believe the schematic, the brake warning circuit does
nothing at all; in '86 they shifted over to monitoring the brake
fluid level and could have but didn't eliminate the fancy
electronics.  It wouldn't have killed them to do both, it seems to
me, especially since they left the electronics in.

It's been stated that at some point they shifted to a single pressure
switch on the brake M/C -- the schematics don't reflect this, and
doing it would mean that partial brake failure (front or rear
circuit) would also eliminate the brake lights if the "wrong" circuit
failed.  Can someone confirm or deny?  I admit I'm too lazy to pull
my panel just to look.

Yours,
David

Yours,
David