Re: Proprtioning valve & ABS

[Brett Dikeman <brett@arthur.malebolge.com>]

At 11:16 AM -0500 on 1/30/98, Phil Payne wrote:


> In message <1029186e.34d1f622@aol.com> C1J1Miller@aol.com writes:
>
> > I know that earlier cars, such as my '91 200q, had an "anti-lock" off
>button
> > on the dash.  Similarly, if you lock the rear diff, it automatically
>disables
> > the antilock.  Seems like some judicious review of the wiring diagram
>from my
> > '91 and your later car could tell you which wire would (temporarily)
>disable
> > the antilock, and allow your testing.  Actually, I like the ability to
>disable
> > antilock, especially up here in NH where it snows...
>
> Nothing easier.  Locate the accelerometer under the rear seat, and pull
>off the
> connector - dead ABS.  Plug it back in, switch the ignition off and on -
>live
> ABS.
I was not aware that any ABS system on the market used accelerometers,
especially since in '90-92 they were very expensive, unreliable, and
innaccurate.  I might expect them in traction control systems nowadays...

I do know for sure that the silver box under the rear seat on a 5000 is the
central control unit(a _very_ pricey little sucker...$700-800!)
When ours had to be replaced, I dissected the bad boy...all sorts of neat
stuff inside, including heavy duty transistors for switching the actuators.
They're _huge_, and use the case as a heatsink...the whole thing, under
that cover, is surrounded by a cage, and that's what is used to sink the
heat.  No accelerometers.

I looked at the mechanic and said "$700?  For that, you could get a whole
desktop computer"
The mech looked at me and said, "which would you rather have on an icy
road, a desktop PC or this thing?" :)

Analog Devices makes a _super_ accurate, completely solid-state
accelerometer that's about the size of a pencil eraser tip.  Wicked cool; I
sent away for a demo kit, and I was really impressed.  Had fun hooking it
up to a big analog meter and driving around...good for little projects such
as tilt sensors, shipping "roughness" sensors(I'm not joking...they
actually make electronic devices that record any bumps or whatnot to a big
expensive item being shipped), and all sorts of other cool things.  Analog
Devices also really wants to use them for airbag sensors, which would be an
excellent idea since these things don't break and have a very high
accuracy/resolution, so they would be ideal for "smart" airbag systems...

Brett

------
Brett Dikeman
brett@pdikeman.ne.mediaone.net
~)-|
Hostes alienigeni me abduxerunt.  Qui annus est?
Te audire non possum.  Musa sapientum fixa est in aure.
Ita, scio hunc 'sig file' veterem fieri.
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