Hi Hugh (et al):
Further testing: With the switch itself (description: two male prongs
on one end and a plunger/nipple on the other) **on the bench** I find:
The two male prongs are electrically connected to each other regardless
of whether the plunger is in or out. When I check continuity with
either prong and the plunger, it's nonexistent until I push the plunger
in and then it's absolute with both. The result is that when I plug in
the connector (the 12V from the brake warning light and one to earth)
to the plunger switch (switch not yet installed in PDWA housing) the
light is on bright (key on) and stays on when the car is started. Same
deal if the switch is installed in the housing.
It strikes me the problem is that the there should be no continuity
between the two prongs until the plunger is depressed. BUT... Have I
perhaps made a mistake in setting up the connection? When I look at the
schematic in Dan Masters' book I see the brake failure switch is an
SPST normally open switch. I have one wire (Black/purple)connected to a
female in the plug (that attaches to the switch) and the other female
connected to earth. Since the two male prongs are connected to each
other, touch male prongs to female connectors and you complete the
circuit at that point. As I understand it, the action of the
off-centred piston is to depress the plunger and complete the ground.
But if that's already happened...
What am I missing?
John
On Sun, 15 Sep 2002 17:18:54 -0400 Hugh Fader <hfader@usa.net>
wrote:
> Hi John.
>
> The PDWA circuit works like this: One side of the warning light is connected
> to +12V. The other side is connected to the PDWA switch. The other side of
> the PDWA switch is connected to ground. When the PDWA is off center, it
> throws the switch which grounds the light to complete the circuit.
>
> I'm not sure where you are checking for continuity. If the switch is in
> place and the PDWA is off center you should measure near zero ohms between
> the connector and ground.
>
> I think the switch ground is the little nipple that goes into the PDWA
> valve. Try measuring between that point and the connector on top.
>
> - Hugh Fader
>
> > -----Original Message-----
> > From: owner-6pack@autox.team.net [mailto:owner-6pack@autox.team.net]On
> > Behalf Of John Griffiths
> > Sent: Sunday, September 15, 2002 2:16 PM
> > To: 6pack@autox.team.net
> > Subject: PDWA Plunger Continuity
> >
> >
> > Hi Folks:
> >
> > I'm working on a '73 TR6. After restoring the wiring between my brake
> > warning light and PDWA and grounding the connector and replacing the
> > missing oil pressure switch (and eventually getting the
> > wiring correct
> > on that, thanks to Nelson Reidel et al)) I've been recently trying to
> > reset the PDWA with no success. I tried the brake bleeding
> > approach and
> > I also tried the brad-awl-where-the-plunger-goes approach. No magic.
> > The light stays bright no matter what I try. If I take the connector
> > off the PDWA, the light glows dimly with the key on. Start
> > the car and
> > the light goes out. That, it seems to me, indicates that I have the
> > connections OK. So... I took the PDWA plunger out and tested the
> > continuity. I'm assuming it should show absolute continuity (zero
> > resistance) at rest (i.e. plunger out) and infinite resistance
> > (showing "1" on the meter) when depressed (or vice versa...). I find
> > that it shows absolute continuity/zero resistance whether "at
> > rest" or
> > depressed. Also I find that if I plug the connector into the plunger
> > unit (thereby connection the two points) the brake light stays on
> > bright with key on and car running. Forgive the naive question but
> > um... have I found my problem (replace the plunger switch)?
> >
> > Thanks.
> >
> > John
>
john.griffiths@uregina.ca
Professor, Dept. of Music,
Development Director, "Mini-University",
Riddell University Centre 256.15,
University of Regina,
Regina, Sask.
S4S 0A2
(306) 585-5534
FAX: (306) 585-5549
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