MAINTENANCE OF M939 SERIES VEHICLES - OD1661 - LESSON 1/TASK 2
Step 4. In this step, SGT Metcalfe is going to measure the battery
resistance.
First, he dials 77 into the TEST SELECT switches and
presses the TEST button. Since the word GO appears on the display,
SGT Metcalfe depresses the starter switch until the word OFF appears
on the display.
The display will change from the word OFF to a
number display.
SGT Metcalfe then compares this number to the
maximum resistance of 13 milliohms.
Since the battery resistance
displayed is greater than the maximum resistance, SGT Metcalfe checks
the electrolyte level, cleans the battery terminals, and tests the
specific gravity of the batteries.
After these steps have been performed, SGT Metcalfe charges the
batteries and repeats the tests. The batteries fail the test again,
indicating that they are defective and should be replaced in
accordance with the procedures contained in paragraph 4-41 of
TM 9-2320-272-20-1.
c.
Charging System Troubleshooting. In the following paragraphs we
will follow SSG Heatherly as he troubleshoots the charging system for
the malfunction NO ALTERNATOR OUTPUT and arrives at the conclusion
that circuit 568 needs to be repaired.
SSG Heatherly begins by reading DA Form 2404 and talking with the
operator.
Once he understands the nature of the malfunction, he
reads through the troubleshooting procedures to determine the tools
and equipment necessary to perform the procedures.
For this
malfunction, SSG Heatherly will need a mechanic's general toolbox and
a multimeter. For the purposes of this subcourse it is assumed that
SSG Heatherly is proficient in the use of a multimeter. Once he has
the necessary tools and equipment, SSG Heatherly configures the
vehicle according to the items cited in paragraphs 3a(1) thru 3a(5)
on page 34 of this task.
Now SSG Heatherly is ready to begin
troubleshooting.
Step 1. The first thing that SSG Heatherly does is check for loose,
broken, or missing alternator belts.
Since all the belts were
present and secure SSG Heatherly will proceed to step 2.
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