TM-9-2320-272-24-1

TRUCK, 5-TON, 6X6, M939, M939A1, AND M939A2 SERIES TRUCKS (DIESEL)

TECHNICAL MANUAL; UNIT, DIRECT SUPPORT, AND GENERAL SUPPORT MAINTENANCE MANUAL; VOLUME 1 OF 4

JUNE 1998

TM-9-2320-272-24-1 - Page 221 of 1015

TM 9-2320-272-24-1

Table 2-3. Electrical Troubleshooting (Contd).

MALFUNCTION

TEST OR INSPECTION

CORRECTIVE ACTION

22. ONE OR MORE TRAILER LIGHTS INOPERATIVE

Test 1. Test trailer receptacle voltage.

Step 1.

Place battery switch to ON position.

CAUTION

Lead 15 or wire 15 is hot whenever the batteries are connected.

Step 2.

Place light switch to position corresponding to inoperative lamp.

NOTE

For stoplight lead test, brake pedal must be depressed and air

pressure maintained.

Step 3.

Set multimeter to 50-volt range.

Step 4.

Connect multimeter negative lead to socket terminal pin L on receptacle. Touch positive

lead to appropriate connector socket of lead being tested. Light switch must be in the

corresponding position.

a.

Battery voltage should be indicated at connector socket being tested.

b.

If voltage was not indicated at one or more of pins being tested, go to test 2.

c. If voltage is indicated, disconnect and reconnect male connector to ensure positive

connection. If trailer lamps still do not light, check male connection for corrosion.

d.

If trailer lamps still do not light, check trailer lighting system.

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