TROUBLESHOOTING THE HMMWV - OD1616 - LESSON 2/TASK 1
current probe. After the engine has been shut down and the current
probe removed, SSG Roberts is directed to check the drive belts.
To check the drivebelt tension, SSG
Roberts is referred to paragraph 3-76, page 3-126 of the TM. Since
the drivebelt tension was correct, he is directed to step 5.
Step 5. Install Test Probe Cable. To install the test probe cable,
remove the access cover to expose the output terminal of the
Now, SSG Roberts connects plug P1 of the test probe cable W2 to jack
J4 on the VTM. After the connections have been made, short the red
and black leads together.
Step 6. Do Test Probe Cable Offset. To perform this procedure, SSG
Roberts first dials 89 into the TEST SELECT switches.
presses and holds the TEST button until the prompting message CAL
appears on the display. At this point, he releases the TEST button
and waits for the offset value to appear on the display. The offset
value should be between -6.8 to +6.8. For this example, it is within
these limits, so SSG Roberts proceeds to the next test step.
Step 7. Check Charging System Output Voltage. To perform this step,
SSG Roberts clips the red lead of cable W2 to the output terminal of
the alternator and the black lead to any suitable ground. Once the
connections have been made, he reconnects the battery ground cable
and starts the vehicle engine. With the engine running, he turns the
vehicle lights and accessories. Once the lights and accessories are
on, he sets the vehicle engine speed to fast idle. Now, he presses
the TEST button. The output voltage should be between 26.5 Volts and
However, upon observing the display, SSG Roberts finds
that the output voltage is only 24 Volts. Therefore, he must proceed
to step 8.