TM-5-3805-254-14-P-2
TRUCK, DUMP, 20 TON, 6X4, ON-OFF HIGHWAY 71,000 GVW, IHC MODEL F-5070 (CCE)
TECHNICAL MANUAL; OPERATOR’S, ORGANIZATIONAL, DIRECT SUPPORT, GENERAL SUPPORT AND DEPT MAINTENANCE MANUAL (INCLUDING REPAIR PARTS INFORMATION AND SUPPLEMENTAL MAINTENANCE INSTRUCTIONS)
JUNE 1980
TM-5-3805-254-14-P-2 - Page 146 of 894
TRUCK SERVICE MANUAL
BRAKES-AIR
Only test gauges known to be accurate are to be
used for checking brake valve delivery pressures,
governor pressure settings and other tests.
Test gauges
differ from ordinary dash gauges in respect to material
and workmanship. Due to these differences they are
more accurate over entire range and maintain their
accuracy over longer periods.
After initial starting of engine, if air gauge shows
that one circuit has no air pressure nor a noticeable
increase in air pressure within a reasonable length of
time (30 to 60 seconds) and the low pressure switch and
low pressure light will not shut off, this indicates an open
drain cock or a failure in the brake system.
NOTE: It is not compulsory but it is advisable that
vehicles be inspected to be sure that the air gauges
are properly connected. The primary system should
be connected to the green needle and secondary
system to red needle.
This can easily be checked by
charging the air system, bleeding off the primary
system (rear brake reservoir) and the green needle
should drop.
If the green needle does not drop the
air lines on the gauge should be changed.
Al
chassis would be assured that they are connected in
the same manner and identification of both systems
will be uniform.
SERVICE CHECKS
1.
Check the air gauge for accuracy.
The simplest way
to do this is to compare the pressures registered by the
gauge over its normal pressure range with the pressure
registered by a test gauge know to be accurate.
2.
A gauge which loses its accuracy must be replaced.
The continued use of a dash gauge showing an error of
more than 5 pounds is not recommended.
LOW PRESSURE INDICATOR (LP3 Type)
DESCRIPTION
The low pressure indicator (Fig.
4) is a safety
device designed to give an automatic warning whenever
the air pressure in the primary or secondary air brake
system is below approximately 70 pounds.
Operating as
an air controlled switch of an electrical circuit, the low
pressure indicator automatically sounds a buzzer when
the air pressure drops too low.
The warning will be both
visible (light) and audible (buzzer).
The nominal pressure setting of 70 pounds is
subject to a tolerance of plus or minus 6 pounds so that
the actual operating pressure of the low pressure
indicator may vary between 76 pounds maximum and 64
pounds minimum.
Back to Top
