MAINTENANCE OF M939 SERIES VEHICLES - OD1661 - LESSON 1/TASK 2
SYSTEMS INOPERATIVE OR WEAK. For the purposes of this subcourse, SSG
Blackwood will troubleshoot this malfunction to the conclusion that
the batteries need to be replaced.
To begin, SSG Blackwood reads DA Form 2404 and talks with the
operator. Once she has a firm idea of the nature of the malfunction,
she reads through the troubleshooting procedures to determine what
tools and special test equipment is needed.
For this particular
malfunction she will need a mechanic's general toolbox, an optical
specific gravity battery tester, a multimeter, and a STE/ICE test
Once the necessary tools and equipment have been gathered
together, SSG Blackwood configures the vehicle according to the items
listed in paragraphs 3a(1) thru 3a(5) on page 34 of this task.
First, SSG Blackwood performs the
following steps to inspect the
(1) Visually check the batteries for cracks, leaks, or corroded
Since no cracks, leaks or corroded terminal posts
are found, SSG Blackwood proceeds to the next item.
(2) Now she checks for loose, broken, or worn terminals and
Since the terminals and cables are not loose, broken, or
worn; SSG Blackwood will proceed to the next item.
(3) In this item, SSG Blackwood checks the electrolyte level in
each battery cell.
Finding the electrolyte level in each cell
adequate, SSG Blackwood proceeds to the next item.
(4) At this point in the troubleshooting procedure SSG Blackwood
uses the optical specific gravity tester to test the specific gravity
of each battery.
They must test 1.225 or greater, temperature
corrected, and each cell in a battery must test within 25 points of
When SSG Blackwood checked the specific gravity she
found it to be at 1.225; however, the cells of the batteries exceeded
the 25 point variation.
This indicates that the batteries are
defective and need to be replaced. The procedures for replacing the
batteries are contained in paragraph 4-24 of TM 9-2320-272-20-1.