TM 5-2350-378-23&P
0004
TROUBLESHOOTING THE HDC SYSTEM - Continued
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 VDC reference voltage
and returns a DC analog voltage between 0.5 VDC and 9.5 VDC to the HDC Control Box representing the hydraulic
pressure measured by the transducer in the circuit.
The hydraulic pressure transducers can also fail in two ways; failure to measure any hydraulic pressure
(complete failure) or failure to accurately measure the hydraulic pressure (producing erroneous measurement
indications) and provide an analog voltage back to the HDC Control Box that is outside of the range of acceptable
voltages (outside the 0.5 - 9.5 VDC range). If the "measured" DC voltage returned to the HDC Control Box from the
pressure transducer is within the acceptable range of 0.5 to 9.5 VDC, regardless of how inaccurate the measurement
may be, the inaccuracy/malfunction cannot be detected by the HDC Control Box as part of the System BIT.
The HDC System Functional Check-Out (WP 0025) addresses many of the HDC System components and fault
isolates most problems/malfunctions associated with those components. For those HDC System solenoid valves
and pressure transducers specified, and those not specifically addressed in the Functional Check-Out, refer to the
applicable maintenance WP to aid in determining if an HDC System solenoid valve or hydraulic pressure transducer
may have failed or malfunctioned, based on possible consequences and symptoms of a malfunctioning or failed
HDC system component.
USE OF THE HDC SYSTEM
The HDC is only used when a problem has been detected (or suspected) in the M9 ACE hydraulic system and formal
troubleshooting of the system is necessary. Before the HDC System is actually used to aid in troubleshooting the
vehicle hydraulic system, the M9 ACE HDC System Functional Check-Out (WP 0025) should be performed to
establish the operational readiness of the HDC System. The HDC system is only used when the vehicle is not moving,
the vehicle is in "neutral" and the parking brake is fully engaged.
GENERAL HYDRAULIC SYSTEM TROUBLESHOOTING PROCEDURES
Refer to TM 5-2350-262-20.
GENERAL
Refer to TM 5-2350-262-20.
GENERAL NOTES
Refer to TM 5-2350-262-20.
Hydraulic troubleshooting can often be reduced by taking the following step:
Instead of replacing an HDC System solenoid valve or pressure transducer, temporarily switch it with a spare item,
or with another identical solenoid valve or pressure transducer.
NOTE
Before attempting to repair or replace any hydraulic component you must:
1. Determine the maintenance responsibility for repair or replacement of the component.
2. If the task is at your echelon of maintenance responsibility, you must identify the tools needed and the
replacement parts required.
Refer to the Maintenance Allocation Chart (MAC) to determine not only the maintenance responsibility of the item,
but also to obtain an estimate of the time required to perform the task, tools needed, and any special notes/
requirements necessary.
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