Chevrolet 70 1969 Series, Shop Manual

Page: 368 / 913

AIR COMPRESSORS AND GOVERNORS 6T-7
AIR COMPRESSOR GOVERNOR
DESCRIPTION
The governor, operating in conjunction with
air compressor unloading mechanism, automati­
cally controls air pressure in the air brake or air
supply system between the desired, predetermined
maximum and minimum pressures. The air com­
pressor runs continually while the engine runs,
but actual compression of air is controlled by the
governor which stops or starts compression when
the maximum or minimum pressures are reached.
MAINTENANCE
Every 500 operating hours or after every
15.000 miles, clean or replace governor filters.
Every 3,000 operating hours or after every
100.000 miles, disassemble the governor and
clean and inspect all parts. Repair governor if
necessary.
GOVERNOR TESTS
O P E R A T IN G T E S T
Start the engine and build up air pressure in
system. Observe reading on air pressure gauge
in gauge panel when governor cuts-out, stopping
compression of air by the compressor. Reading
on gauge when governor cuts-out should be within
range shown on "Governor Adjustment Chart.”
With the engine still running, slowly reduce
air pressure in the system by applying and re­
leasing brakes. Observe pressure registered by
gauge when governor cuts -
in and compression is
resumed. Gauge reading should be within range
shown on “ Governor Adjustment Chart.”
Before condemning or adjusting the governor,
be sure the dash air gauge is registering ac­
curately. Use an accurate test gauge to check
pressure registered by the dash gauge. If the
pressure settings of the governor are inaccurate
or it is necessary that they be changed, adjust
governor as described below under “ Governor
Adjustment Chart. ”
L E A K A G E T E S T
Leakage checks on the governor are made at
its exhaust port in both cut- in and cut-out posi­
tions. In the cut-in position, check exhaust port
for inlet valve leakage by applying a soap solution
at the port. Leakage could also be past the bottom
piston grommet (B-W only). In the cut-out posi­
tion check the exhaust port to determine if leakage
is present at the exhaust valve seat or stem
grommet. In this position leakage could also be
past the upper piston grommet (B-W only).
If there is excessive leakage, overhaul
governor.
GOVERNOR ADJUSTMENT
The following procedure covers adjustment
with compressor installed on vehicle. Governor
is mounted on a bracket which is attached to com­
pressor cylinder head or block, dependent upon
model.
GOVERNOR ADJUSTMENT CHART
G O V E R N O R
CUT-IN
CUT- OUT
All Midland-Ross . .
85 psi
100-107 psi
All Bendix-Westing-
house except below .
86-90 psi
103-111 psi
B endix- Westinghouse
compressors 280094,
280095, 280367, and
280368 ......................
102-108 psi
123-131 psi
Bendix-Westinghouse
compressor 280500 .
98-104 psi 118-126 psi
M IDLAN D- R OSS (Fig. 9)
1. Loosen lock nut. Use screwdriver at ad­
juster plug.
2. Turn adjuster plug in (clockwise) to in­
crease cut-out setting, or out (counterclockwise)
to decrease setting. One complete turn of adapter
plug will change cut-out pressure 20 psi.
3. When cut-out pressure setting of 100-107
psi is attained, lock adjuster plug with lock nut.
BE N D IX - W ES T IN G H O U S E (Fig. 10)
1. Unscrew rubber cover and remove it from
the governor.
2. Loosen adjusting screw lock nut.
3. Using a screwdriver, turn adjusting screw
counterclockwise to raise pressure settings. Turn
adjusting screw clockwise to lower the pressure
settings.
4. When adjustment is completed, tighten ad­
justing screw lock nut.
5. Install cover on the governor.
GOVERNOR REPLACEMENT
The following procedures apply to all
governors on both Midland-Ross and Bendix -
Westinghouse air compressors.
R E M O V A L
1. Exhaust air from system.
CHEVROLET SERIES 70 -80 H EAVY DUTY TRUCK SH O P M A N U A L