MAINTENANCE OF M939 SERIES VEHICLES - OD1661 - LESSON 1/TASK 2
direction of the negative post connected to the cable.
The test probe cable W2 is first connected to battery A for testing
battery A.
The test probe cable W2 is then connected to battery B for testing
battery B.
The current probe is in the same place as for testing
battery A.
To test battery C or D, clamp the current probe around the cable
connecting battery C and battery D. Point the arrow on the current
probe in the direction of the negative post connected to the cable.
The test probe cable W2 is then connected to battery C for testing
battery C.
The test probe cable W2 is then connected to battery D for testing
battery D.
After attempting to crank the engine for several cycles, SGT Metcalfe
turns off all vehicle electrical power and dials 90 into the TEST
SELECT switches. He then presses and holds the TEST button until the
CAL message appears on the display.
When the CAL message appears,
SGT Metcalfe releases the TEST button and waits for the offset value
to appear. The offset value should be between -225 and +225, which
it was. Therefore, SGT Metcalfe will proceed to step 3 and measure
the battery resistance change.
Step 3. To measure the battery resistance change, SGT Metcalfe first
dials 79 into the TEST SELECT switches. Then he presses and releases
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.
Once the again the display changes, this time
displaying a number.
SGT Metcalfe compares the number displayed (15), with the amount of
maximum resistance change, which is 25 milliohms per second.
Since
the displayed battery resistance change is less than the maximum
resistance change, SGT Metcalfe proceeds to step 4.
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