MAINTENANCE OF M939 SERIES VEHICLES - OD1661 - LESSON 1/TASK 2
Trailer Connection System Troubleshooting.
In the following
paragraphs we will follow SGT Markum as he troubleshoots the trailer
NOT FUNCTION ON THE TRAILER and reaches the conclusion that one of
the trailer connecting cables is defective and needs to be repaired.
DA Form 2404 and talking with the operator.
He reads the
troubleshooting procedures to determine the required tools, and
configures the vehicle according to the items cited in paragraphs
3a(1) thru 3a(5) on page 34 of this task.
As a result of these
troubleshoot this malfunction.
The first step requires SGT Markum to test the trailer
connecting receptacle voltage.
In order to perform this test, SGT
Markum is required to perform the troubleshooting procedures for the
malfunction ONE OR MORE TRAILER LIGHTS INOPERATIVE.
(1) Troubleshooting Procedure for the Malfunction ONE OR MORE
TRAILER LIGHTS INOPERATIVE, Step 1. First, SGT Markum must test the
trailer receptacle voltage.
This is accomplished by placing the
battery switch to the ON position and placing the light switch to the
corresponding position for the inoperative lamp.
For stoplight circuit test, the brake pedal must
be depressed and air pressure maintained.
SGT Markum now sets the multimeter to the 50 volt range and connects
the negative meter lead to the socket terminal pin L as shown in
figure 27 (on the following page).
He then touches the positive
meter lead on the appropriate connector socket of the circuit being
The light switch must be in the corresponding position.
Since battery voltage is indicated, SGT Markum will proceed to
troubleshooting step 2.