Subject: Re: [6pack] PDWA - Pressure Differential Warning Actuator

From: John Cyganowski via 6pack <[email-masked]>
Date: Tue, 6 Aug 2019 18:46:01 +0000 (UTC)

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 I will toss in a few more cents to this discussion.=C2=A0
Firstly, what is this thing and what does it do? =C2=A0I have heard =E2=80=
=9Cregulator=E2=80=9D, =E2=80=9Cbrake circuit balancer=E2=80=9D or =E2=80=
=9Cvalve=E2=80=9D etc. =C2=A0It is none of these. It is a pressure switch. =
Period. It is a part of a safety system to alert the driver of an unsafe co=
ndition in the brake system. It is one the few safety system in these cars.=
 One side of the switch is open to the front brake circuit and the other si=
de of the switch is open to the rear brake circuit. There is a cross over t=
hat contains a metal shuttle. When the driver steps on the brakes, if the p=
ressure in one circuit is lower than the pressure in the other circuit, the=
 shuttle moves toward the low pressure circuit depressing the switch mounte=
d on the cross over establishing a ground and lighting the brake fault ligh=
t.=C2=A0
The front and back circuits are Isolated by seals on the shuttle. There are=
 2 types of PDWAs. One uses double o-ring seals on each side of the shuttle=
 to prevent a fluid leak and to allow pressure to be maintained in the circ=
uit. The replacement o-rings are available from the usual suspects. This is=
 the most common type of pressure switch. There is another type with seals =
that are like little moulded rubber cups mounted ends of the shuttle. I don=
=E2=80=99t know if these seals are still made.
Like any seal they can get old and disintegrate (they swell with contact to=
 glycol based brake fluids) and they should be replaced. It is a very simil=
ar with wear components like the brake pads and shoes. They wear out and ha=
ve to be replaced. When the seals fail, the individual circuits do not inte=
rmix. Because the brake circuits are both under pressure, the fluid looks f=
or the path of least resistance and it leaks out the threads of the actuato=
r switch. The leaking fluid will eat your paint quick undiscovered.=C2=A0
It is neither hard nor difficult to remedy the seals in the PDWA and keep a=
 working safety system that could possibly save your life or the life of yo=
ur passenger. =C2=A0But it is your car and we all have our own threshold of=
 risk. I think it is irresponsible to recommend that someone make modificat=
ions to defeat a safety system on a mission critical system like brakes. =
=C2=A0YMMV.=C2=A0
John Cyg70 DamsonCC9252LO

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<html><head></head><body><div class=3D"ydp9ab9db8ayahoo-style-wrap" style=
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;"><div></div>
        <div>I will toss in a few more cents to this discussion.&nbsp;</div=
><div><br></div><div>Firstly, what is this thing and what does it do? &nbsp=
;I have heard =E2=80=9Cregulator=E2=80=9D, =E2=80=9Cbrake circuit balancer=
=E2=80=9D or =E2=80=9Cvalve=E2=80=9D etc. &nbsp;It is none of these. It is =
a pressure switch. Period. It is a part of a safety system to alert the dri=
ver of an unsafe condition in the brake system. It is one the few safety sy=
stem in these cars. One side of the switch is open to the front brake circu=
it and the other side of the switch is open to the rear brake circuit. Ther=
e is a cross over that contains a metal shuttle. When the driver steps on t=
he brakes, if the pressure in one circuit is lower than the pressure in the=
 other circuit, the shuttle moves toward the low pressure circuit depressin=
g the switch mounted on the cross over establishing a ground and lighting t=
he brake fault light.&nbsp;</div><div><br></div><div>The front and back cir=
cuits are Isolated by seals on the shuttle. There are 2 types of PDWAs. One=
 uses double o-ring seals on each side of the shuttle to prevent a fluid le=
ak and to allow pressure to be maintained in the circuit. The replacement o=
-rings are available from the usual suspects. This is the most common type =
of pressure switch. There is another type with seals that are like little m=
oulded rubber cups mounted ends of the shuttle. I don=E2=80=99t know if the=
se seals are still made.</div><div><br></div><div>Like any seal they can ge=
t old and disintegrate (they swell with contact to glycol based brake fluid=
s) and they should be replaced. It is a very similar with wear components l=
ike the brake pads and shoes. They wear out and have to be replaced. When t=
he seals fail, the individual circuits do not intermix. Because the brake c=
ircuits are both under pressure, the fluid looks for the path of least resi=
stance and it leaks out the threads of the actuator switch. The leaking flu=
id will eat your paint quick undiscovered.&nbsp;</div><div><br></div><div>I=
t is neither hard nor difficult to remedy the seals in the PDWA and keep a =
working safety system that could possibly save your life or the life of you=
r passenger. &nbsp;But it is your car and we all have our own threshold of =
risk. I think it is irresponsible to recommend that someone make modificati=
ons to defeat a safety system on a mission critical system like brakes. &nb=
sp;YMMV.&nbsp;</div><div><br></div><div>John Cyg</div><div>70 Damson</div><=
div>CC9252LO</div><div><br></div></div></body></html>
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