You have an '82 diesel? Looking at that in Bentley.....
S8 supplies constant (battery) + to brake switches via a red/yellow wire.
This wire enters one switch connector then splits off to the other.
You should see constant 12 volts at each yellow/red wire.
In a similar manner, a red/black wire goes from one switch connector to the
other,
becoming 1 red/black wire which carries + to brake lights when either
switch closes.
You should see 12 volts at either wire when brake pedal pushed down.

Suggestions:
(likely NOT the cause) test brake lights with brake warning light
disconnected.
Test brake lights with one switch plugged in at a time.
Test brake lights while moving wires to switches.

Ground is constant.
FWIW brake light ground is at "in connection box"
..... whatever that means.  ;)

Neil.

On Fri, Oct 9, 2015 at 10:23 AM, Jim Felder <jim.felder@gmail.com> wrote:

> Another thing, if anyone is so inclined to do so, I need to understand how
> the switches are supposed to work. It looks to me like there is always
> power to the switch, and the pressure interrupts the ground, which is the
> bottom of the U-shaped arrangement of terminals, the two opposing terminals
> being red and red yellow wires, so maybe it is the ground wire I need to
> chase down?
>
>
>
> On Fri, Oct 9, 2015 at 11:43 AM Jim Felder <jim.felder@gmail.com> wrote:
>
> > Bought two new switches this morning and installed them. No brake lights.
> > When the connectors are jumpered (the two opposing positions) both brake
> > lights come on. Getting power to them obviously. What else could be
> wrong?
> > Still out there with a voltmeter and a bentley, trying to make sense of
> > both. If the brake light switch connectors are getting power, and the
> > lights come on when the power is jumpered, and the old parts were new,
> and
> > the new parts are newer, then what else could there be that keeps these
> > lights from actuating? I just don't get it.
> >
> > Jim
> >
> > On Fri, Oct 9, 2015 at 10:36 AM John Rodgers <jrodgers113@gmail.com>
> > wrote:
> >
> >> My experience with the lights when not working has been to take each
> >> fixture apart and clean the heck out of the connections getting rid of
> any
> >> rust and corrosion. Made sure there was good metal to metal contact
> where
> >> needed. Cleaned all lenses and lubed the seals with a little silicon
> >> lubricant, then reassembled them.
> >>
> >> Never dealt with a switch failure. That's a whole 'nother horse!
> >>
> >> John
> >> On Oct 8, 2015 20:43, "Stuart MacMillan" <stuartmacm@gmail.com> wrote:
> >>
> >> > I’ve had way too many of these fail.  And, for some reason, they seem
> to
> >> > fail at the same time.  Supposedly, if only one fails the brake
> warning
> >> > light should go on when you apply the brakes, but that has never
> >> happened.
> >> > Aftermarket suppliers can’t seem to make switches that can take high
> >> > pressure for very long. If the dealer still sells them get them there,
> >> they
> >> > are just too important to take chances.
> >> >
> >> >
> >> >
> >> > Stuart
> >> >
> >> >
> >> >
> >> > From: Jim Felder [mailto:jim.felder@gmail.com]
> >> > Sent: Thursday, October 08, 2015 3:13 PM
> >> > To: Stuart MacMillan; vanagon@gerry.vanagon.com
> >> > Subject: Re: Help me diagnose and fix no brake lights
> >> >
> >> >
> >> >
> >> > I have the three-pin connectors, but shorting the facing two causes
> the
> >> > brake lights to work. This isn't among the last work done, it was done
> >> two
> >> > years ago when I did the brakes and suspension. That's not a very long
> >> life
> >> > for a brake switch, in my opinion. I wish I could remember when I got
> >> them
> >> > from so I wouldn't make the same mistake twice.
> >> >
> >> >
> >> >
> >> > Thanks, all. I'll let you know if the new new switches work, but I'm
> >> > pretty sure that's going to be it.
> >> >
> >> >
> >> >
> >> > Jim
> >> >
> >> >
> >> >
> >> > On Thu, Oct 8, 2015 at 3:54 PM Stuart MacMillan <stuartmacm@gmail.com
> >
> >> > wrote:
> >> >
> >> > First, short the two wires on each switch together and see if the
> lights
> >> > go on.  If not, it's likely wiring, if they do, it's the switches.
> >> Replace
> >> > both of them. It's not uncommon for these to fail.
> >> >
> >> > Stuart
> >> >
> >> > -----Original Message-----
> >> > From: Vanagon Mailing List [mailto:vanagon@gerry.vanagon.com] On
> Behalf
> >> > Of Jim Felder
> >> > Sent: Thursday, October 08, 2015 12:27 PM
> >> > To: vanagon@GERRY.VANAGON.COM
> >> > Subject: Help me diagnose and fix no brake lights
> >> >
> >> > Daughter was driving behind me in the Westy today and called me to say
> >> > neither brake light was coming on. All other lights working. Brakes
> >> > excellent, newish MC and brake light switches.
> >> >
> >> > All fuses look good. Where should I start looking?
> >> >
> >> > Thanks in advance for your help. I need to head out of town overnight
> >> next
> >> > friday.
> >> >
> >> > Best,
> >> >
> >> > Jim
> >> >
> >>
> >
>

-- 
Neil n

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