Chevrolet 10 Series 1968, Service Manual

Page: 315 / 713

BRAKES 5-72
Installation
Position valve in place with arrow on side of body in­
dicating direction of air flow. Secure air lines to each
end of the valve.
Testing Rebuilt Unit
Both operation and leakage tests must be made as out­
lined under Service Checks--Single Check Valve.
LOW PRESSURE INDICATOR SWITCH
Rem oval
1. Make certain ignition is off.
2. Exhaust all air from brake system.
3. Disconnect the electrical connections at the low
pressure indicator switch.
4. Disconnect the air line to the low pressure indicator
switch.
Installation
1. Mount indicator in place.
2. Attach and tighten mounting nut and connect air line.
3. Attach and tighten electrical connection.
Testing Replacement Unit
Both operating and leakage tests must be made as out­
lined under Service Checks—Low Pressure Indicator.
AIR GAUGE
Rem oval
1. Remove air line and lamp socket.
2. Remove four instrument panel backing plate screws
and remove backing plate from vehicle.
3. Separate gauge from backing plate by removing two
retaining screws.
Testing Replacement Unit
The simplest way to test any dash pressure gauge is to
compare it with a special test gauge that is know to be
accurate. By substituting one gauge for another at one
given point in the air brake system, this comparison can
be made.
Installation
1. Attach gauge to instrument panel backing plate using
original screws or equivalent.
F ig . 110-Pressure Protection V a lve -C ro ss Section
2. Mount backing plate-gauge assembly in instrument
panel.
3. Replace lamp socket and gauge line.
4. Thoroughly check gauge connection for leakage.
PRESSURE PROTECTION VALVE ((Fig. 110)
Disassem bly
1. Remove four screws and separate the upper and
lower bodies.
2. Remove diaphragm, spring cap and spring.
Cleaning and Inspection
1. Wash all parts in cleaning fluid.
2. Inspect diaphragm for cuts and punctures. Some
indentation of the diaphragm by the seat in the lower
body is normal.
Assem bly
1. Position diaphragm, spring cap and spring on lower
body.
2. Align upper body with lower body, install four screws
and secure.
TRAILER EQUIPMENT (DD3)
GENERAL DESCRIPTION
For 1968 trailer air brake equipment is available for
some models. The option includes a hand control valve,
double check valve, emergency air valve, breakaway
valve, trailer connectors, separate stop light switch and
connecting lines (fig. 111). Testing and servicing of these
units is outlined in this section.
OPERATION TEST AND LEAKAGE TESTS
HAND CONTROL VALVE
Operating Tests
1. Check the delivery pressure of the valve, using an
accurate test gauge connected to the trailer brake
service line at the back of the cab. With air system
fully charged, and with valve operating handle in
fully applied position, test gauge should show the
same pressure (within 5 pounds) as registered on the
dash air gauge.
UPPERBODY
SPRING
SPRING CAP
DIAPHRAGM
LOWER BODY
CHEVROLET TRUCK SERVICE MANUAL