TM-5-2350-378-24-P
HYDRAULIC DIAGNOSTIC CENTER (HDC) SUPPORTING ARMORED COMBAT EARTHMOVER (ACE), M9
TECHNICAL MANUAL; UNIT, DIRECT SUPPORT, AND GENERAL SUPPORT MAINTENANCE MANUAL INCLUDING REPAIR PARTS AND SPECIAL TOOLS LIST
TM-5-2350-378-24-P - Page 60 of 790
TM 5--2350--378--24&P
0005 00--1
USING THE HYDRAULIC DIAGNOSTIC CENTER (HDC) SYSTEM TO
TROUBLESHOOT THE M9 HYDRAULIC SYSTEM
0005 00
INTRODUCTION
This Work Package contains information needed when troubleshooting the M9 ACE Hydraulic System using the
Hydraulic Diagnostic Center (HDC) System. It includes information for preparing the HDC System for use and
procedures for performing a Functional Check--Out of the HDC System, both as a weekly PMCS check of the
HDC System integrity, and as the initial step in using the HDC System to aid in troubleshooting the M9 ACE
hydraulic system.
This work package describes the differences between troubleshooting the ACE hydraulic system with, and
without, the HDC System, and explains the additional items that need to be considered when using the HDC
System to aid in troubleshooting the vehicle hydraulic system. Information as to how to use the HDC System to
aid in troubleshooting the M9 ACE Hydraulic System is included as well as information to aid in troubleshooting
the specific HDC System hydraulic and electrical circuits. When used with the HDC system troubleshooting work
package (WP 0022 00).
The HDC System is an aid, used to assist in the troubleshooting of the M9 ACE hydraulic system. The HDC is not
an independent diagnostic tool; it does not provide an automated or semi--automated means of localizing
hydraulic faults. The use of the HDC System allows the amount of time required to isolate faults and malfunctions
in the vehicle hydraulic system to be dramatically reduced, when compared to the time required to troubleshoot
the vehicle hydraulic system without the HDC System.
TROUBLESHOOTING THE HDC SYSTEM
Using the HDC System does introduce some additional factors that should be considered when troubleshooting
the vehicle hydraulic system. Components of the HDC System are located throughout the ACE vehicle and,
although they simplify the actual troubleshooting process, they also introduce additional components that interface
with the previously existing vehicle hydraulic system, that also can fail or malfunction like any other component.
To aid in the troubleshooting of the ACE hydraulic system, the HDC System must be operating properly, and there
must be some way to assess the operational status of the HDC System. The M9 ACE HDC System Functional
Check--Out on the following pages provides the means for the maintainer to easily check portions of the HDC
System to determine if the HDC System is functionally operational.
When the HDC System is to be used (for troubleshooting the vehicle hydraulic system or when just being
functionally checked as part of a PMCS requirement), the M9 ACE HDC System Functional Check--Out should
first be performed. If the HDC System does not pass all portions of the Functional Check--Out, refer to (WP
0022 00) and proceed to troubleshoot the HDC System as indicated.
Aside from the HDC Control Box and three electrical cables integrated into the vehicle, two main types of
components comprise the HDC System; solenoid valves and hydraulic pressure transducers. Although both of
these types of components are very reliable (as are the electrical cables), they can possibly fail like other electrical
and hydraulic components. The solenoid valves are spring--loaded and can possibly fail in two ways. They can
fail to energize, and they can fail to return to the original de--energized state (valve spool does not return to the
de--energized state), when the energizing (supply) voltage is removed. The probability of a solenoid valve being
stuck (the valve spool does not return to the de--energized position) is very low and would only occur after a
hydraulic maintenance test was performed in which the valve had been energized. The actual movement (or
non--movement) of the valve spool cannot be detected by the HDC Control Box as part of the System BIT. The
solenoid valves are normally not energized. They are only energized upon command, and are supplied 24 VDC
only when energized. Normally all solenoid valves are de--energized (reset) and are not supplied any voltage.
When the HDC System is operating, a reference voltage is always supplied to the hydraulic pressure transducers
from the HDC Control Box and the respective hydraulic pressure measured by the individual pressure transducers
is displayed on the HDC Control Box upper LCD. The pressure transducer is supplied a 15 V DC reference
voltage and returns a DC analog voltage between 0.5 V DC and 9.5 V DC to the HDC Control Box representing
the hydraulic pressure measured by the transducer in the circuit.
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