Date: Thu, 5 Jun 2003 23:35:09 -0400
Reply-To: David Beierl <dbeierl@ATTGLOBAL.NET>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: David Beierl <dbeierl@ATTGLOBAL.NET>
Subject: Re: Correlation of brake switch to blinking Temp LED?
In-Reply-To: <20030606005502.609C529999@xmxpita.excite.com>
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At 08:55 PM 6/5/2003, Mark G wrote:
>I notice that once in a great while, when sitting at a stop light in my 87
>Westy automatic, the temp LED will blink for a half second or so just as I
>slightly let off the brake and hear a little 'click' from the brake
>switch, like when moving forward a couple of feet or so...
>
>The light goes out as soon as the brake pedal is either completely
>released or pushed back in. Are these on the same circuit? Will a new
>switch help? It seems odd that the switch sometimes makes that little
>'clicking' noise and sometimes doesn't. (And that the LED only blinks when
>the clicking happens.) Any thoughts? Thanks.
I may be overlooking something obvious -- I dunno. I started looking at
the circuits for the brake warning light, and to my astonishment I can't
find an indication in '87, '90, '83-84 or '81 diagrams of any actual
warning of brake failure. All years have a handbrake warning, and sometime
between '84 and '87 they added a low-fluid warning, but I can't find any
excessive-travel or pressure-difference warning at all. IF that's correct
(and most likely even if it's not, actually) that system should have
nothing to do with what you are seeing.
There are only two ways I know to make that light blink, other than gauge
failure -- reduce the supply voltage below the regulated minimum 9.5 volts,
or apply (even for a fraction of a second) a load on the temp sender line
that would if maintained bring the gauge to full scale. The thing that
seems likeliest to me is that one of two wires is occasionally being
shorted -- the gauge sender line to ground, or the low-level warning
controller input line either to ground or +12 (or strictly speaking to any
fixed voltage at all). I would be inclined to identify those [3] wires
(the gauge sender line is twinned, one to the sender and one from the
low-coolant controller module), and make see if there's any way they could
be getting involved in the brake mechanism.
Failing that, the next time it happens *don't move your foot* and see what
fuse blows, then fix that circuit. That may not be entirely prudent. I
might consider rigging a latching indicator of some sort that would light
up and stay lit if the panel regulated supply fell below 9.5 volts...
The once in a great while thing is the killer. But if it isn't a short
somewhere, most likely to ground, I'm stumped. Or an open on the
level-warning input line would do it. An open on the panel supply would
would too, I guess, maybe -- if it went on for long you'd see the gauges
dropping and such, and your indicator lights would flicker.
Don't like any of these answers -- sell it to your brother and buy it back
after he fixes it.
:(
d
--
David Beierl - Providence RI USA -- http://pws.prserv.net/synergy/Vanagon/
'84 Westy "Dutiful Passage"
'85 GL "Poor Relation"
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