In a message dated 01-10-21 14:59:30 EDT, pleask@telus.net writes:
<< My TVR 2500M has the TR6 running and braking gear. Part of the braking
gear is
the "Pressure differential warning" do-dad that receives the two brake lines
from the servo and distributes the brake lines to each wheel.
In the middle of this cast unit is the plastic electrical switch that will
light up a dash light if there is a brake failure. When I pressurized the
system with air there was a leak around the threads of this plastic switch,
and I have been unable to find another switch. So I took a standard bolt with
a copper washer and put it in place of the plastic switch.
Question: If there was/is an air leak would this allow brake fluid to leak
out
as well ? (Don't know the interior workings of this thing)
Question: How does this unit work ?
Question: There is a metal ball (bearing) at the base of this plastic switch,
is it supposed to be depressed by the plastic electrical switch all the time,
and if there is a brake failure this ball pushes on the switch to indicate
there is a problem or the other way around ?
Question: As I have placed a bolt in here instead of the plastic switch have
I
effectively caused this unit to think it has a brake problem and cut of half
?
Thanks everyone.
Pat >>
Pat-
The PDWA switch is a double ended piston with a depression in the middle.
Each end of the piston is exposed on of the two braking hydraulic circuits
(front and rear).
Under normal use when the brake pedal is depressed the same pressure will act
on both ends of the piston and it will remain centered. If there is a leak
in one circuit the pressure on that end will be less and the piston will move
in that direction.
The electric switch rides on that ball bearing which rides in the piston's
depression. When the piston moves either way the ball bearing rides up out
of the depression and pushes the switch up which activates it and the warning
light. The depressed area of the piston is sealed from the braking system's
fluid by o-rings on each end of the piston. To allow fluid in this area
would defeat the PDWA's purpose.
Whenever you replace your system's fluid and bleed it you should re-center
the PDWA piston- usually by sticking a small screwdriver into the switch hole
and pushing the piston. Your removal of the switch will not cause the light
to be on but I don't know if having the piston in a non-centered position
will affect your braking. I recommend centering it. I hope the bolt you
used had the same thread pattern as the switch.
Larry Bickel
71 2500 #1948T
///
/// tvr@autox.team.net mailing list
///
|