Chevrolet Light Duty Truck 1973 Service Manual page 275

Fig. 13--Hold-Off and Blend Pressure
Fig. 14 -Rear System Failure
found in any portion of the valve, the complete valve
assembly must be replaced.
BRAKE TRAVEL WARNING SWITCH (FIG.
17)
Vehicles with frame mounted vacuum over hydraulic
boosters have an electrical switch that senses pedal
travel. This switch will illuminate the lamp on the
instrument panel whenever the brake pedal travel is in
excess of 5.10 inches.
BRAKE STOPLAMP SWITCH
The brake stoplamp switch is mounted on a flange
protruding from the brake pedal support bracket below
FROM MASTER CYLINDER REAR OUTLET
the instrument panel (fig. 18). When the brake pedal is
depressed, the switch plunger (which is spring loaded),
follows the brake pedal arm downward until the switch is
in the "O N " position. When the brake is released, the
brake pedal arm returns the switch plunger to the
"O FF" position.
BRAKE PEDAL
The brake pedal is a lever, pivoted at one end, with the
master cylinder push rod attached to the pedal near the
pivot point. By this lever arrangement the force applied
to the master cylinder piston through the push rod is
multiplied several times over the force applied at the
brake pedal (fig. 19).
Proper service of the brake pedal is vital to good brake
performance, and pedal operation should be checked
each time brakes are inspected. Weak or broken return
springs or lack of lubrication can cause sluggish release
BRAKES 5-9
LIGHT DUTY TRUCK SERVICE MANUAL