MAINTENANCE OF M939 SERIES VEHICLES - OD1661 - LESSON 1/TASK 2
Starting System Troubleshooting. In the following paragraphs we
will follow SGT Metcalfe as he troubleshoots the starting system for
the malfunction STARTER MOTOR INOPERATIVE and reaches the conclusion
that the starter motor and solenoid are defective and need to be
Again, as in every other troubleshooting task, SGT Metcalfe reads DA
Form 2404 and talks with the operator.
Then he reads through the
troubleshooting procedures to determine the necessary tools and
equipment required to perform the troubleshooting procedure.
this malfunction, he will need a mechanic's general toolbox,
After these have all been
gathered together at the vehicle, SGT Metcalfe configures the vehicle
according to the items listed in paragraphs 3a(l) thru 3a(5) on page
34 of this task. After the vehicle has been configured accordingly,
SGT Metcalfe is ready to troubleshoot.
The first thing that SGT Metcalfe does, since a STE/ICE test set is
available, is perform No-Go test 50. This particular test tests the
charging circuit. For the purposes of this subcourse, it is assumed
that the STE/ICE test set is properly connected.
No-Go Test 50.
Ensure that the vehicle engine is off.
Step 1. The first step in performing No-Go test 50 is to check the
drive belts. The procedure for checking the drive belts can be found
in paragraph 4-8 of TM 9-2320-272-20-1.
Since the drive belts
checked okay, SGT Metcalfe will proceed to step 2 and check the
charging system output voltage.
Step 2. After the drive belts have been checked, SGT Metcalfe starts
the engine and turns on the vehicle lights.
Once the engine
is started and the lights are on, SGT Metcalfe sets the engine
speed to fast idle, dials 89 into the TEST SELECT switches, and
presses the TEST button. The VTM display indicates a voltage reading
that should be between 26.5 and 29.5 volts.
In this instance the