MAINTENANCE OF M939 SERIES VEHICLES - OD1661 - LESSON 1/TASK 2
meter lead to the disconnected circuit 570 wire and the negative
meter lead to ground.
He places the battery switch to the ON
position, cranks the engine, and depresses the ether start switch
while observing the meter.
Since battery voltage is indicated, SGT
Ritz has determined that the ether valve is defective and needs to be
The procedure for replacing the ether valve is contained
in paragraph 4-15 of TM 9-2320-272-20-1.
Indicator, Gage, and Warning System Troubleshooting.
following paragraphs we will follow SSG Gilbert as he troubleshoots
the indicator, gage, and warning system for the malfunction LOW AIR
PRESSURE WARNING BUZZER INOPERATIVE (AIR PRESSURE GAGES INDICATES
SYSTEM PRESSURE) and reaches the conclusion that pressure switch B is
defective and needs to be replaced.
As in all the previous troubleshooting procedures, the first thing
that SSG Gilbert does is read DA Form 2404 and talk to the operator.
Once he has verified the existence of the malfunction, he reads
through the troubleshooting procedures to determine what tools will
be required to accomplish this task.
For this particular
troubleshooting malfunction, SSG Gilbert will need a mechanic's
general toolbox and a multimeter. Once the necessary tools have been
gathered together, SSG Gilbert configures the vehicle according to
the items listed in paragraphs 3a(l) thru 3a(5) on page 34 of this
task. Now that these preliminary procedures have been completed, SSG
Gilbert is now ready to begin the actual troubleshooting procedures.
In this test SSG Gilbert will test the low air pressure
Ensure that the air pressure, is BELOW 60 psi
when testing the warning buzzer.
First, SSG Gilbert places the battery switch to the ON position
and the starter switch to the RUN position.
He notes that
the low air pressure warning lights.
Since the low air
pressure warning light was illuminated, SSG Gilbert proceeds to