Peter,
I wrote the article regarding rebuilding the PDWA and I don't think tripping
the switch will close off either brake circuit. There's room around the
piston(s) for the brake fluid to flow even when the PDWA has been tripped.
On early units (with a screw cap on both ends) you'll have to follow the
instructions in the manual. Open the bleed screw slightly and sloooowly push
the brake pedal. If the pedal continues smoothly to the floor, close the
bleed valve and repeat the procedure on the other circuit. While you press
slowly, you should be able to feel a little "bump" as the pedal goes down, as
the PDWA switch pin re-engages the reduced area in the piston. If you remove
the switch from this type of unit, be careful, there's a tiny ball bearing in
some of these units, between the switch pin and the sliding piston. If this
ball is lost, the PDWA will not work. This type ususally has a grounding wire
wrapped around the threads on the switch.
If you have a later model (with a single end cap), you can remove the switch
and look into the resulting hole. You should be able to see to which end the
piston has moved--the reduced area of the piston should be centered. While
you've got the switch out, take a pointed 1/4" wooden dowl (stick it into a
pencil sharpener and then blow off the shavings) and carefully lever the
piston back to center. Put the switch back in and head on down the road.
Hope that helps,
Charlie B.
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