SM07-017-0
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DESCRIPTION
A stop light switch is installed in the No. 1 circuit of
the dual brake valve. The switch senses the pressure
in the brake air lines. Electrically, the switch is con-
nected to illuminate the stop lights on the rear of the
machine when the brake pedal is depressed. The
switch is an electro-pneumatic switch and is not a
serviceable item. It must be replaced as a complete
assembly.
Stop Light Switch Cutaway
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THEORY OF OPERATION
When a brake application is made, air pressure from
spring snaps a shorting bar which mates with the
the brake valve enters the cavity below the diaph-
contact strips.The stop light electrical circuit is com-
ragm. The air pressure below the diaphragm moves
pleted, lighting the stop lights before the brake appli-
the piston until it contacts the leaf spring. The leaf
cation pressure reaches 6 psi (41 kPa/0.41 bar).
spring travels past a fulcrum at which point the leaf