DeTomaso Mailing List: April 99, Message #127

-- [ From: forest * EMC.Ver #2.5.3 ] --

I just can't let this misconception go on any longer. The brake
differential pressure switch is just that, a switch. It does not block
flow from a broken or ruptured system. When the brake pedal is depressed
the master cylinder pressurizes both the front and rear systems. If one
or the other system fails to hold pressure the higher pressure on the
good side causes the swicth shuttle to move toward the low pressure side
To reset the switch after corrections have been done you need to bleed
pressure from the side that was good so the switch will move back to
center position. Sometimes it requires that you really hit the pedal
hard without opening any bleeders. The point is that this is just a
differential pressure switch and it will not block flow to anywhere and
there is nothing gained by removing it nor is there anything really lost
by removing it entirely as you will know if one half of your brake
system fails by the sudden loss of pedal. Do not however just remove the
guts of the switch as you will then have removed your dual system and
any brake failure now becomes a TOTAL failure. If you want to remove it
then get the appropriate tees and fittings and keep your front and rear
systems separate. You will then have to do something different for a
brake light switch also. I don't know why anyone would want to go to all
this trouble.