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 253 of 1015

TM 9-2320-272-24-1

Table 2-3. Electrical Troubleshooting (Contd).

MALFUNCTION

TEST OR INSPECTION

CORRECTIVE ACTION

HEATER SYSTEM

37. HEATER WILL NOT OPERATE WITH SWITCH IN LOW POSITION (HIGH POSITION OPERATION NORMAL)

Test 1. Test lead 569A for voltage.

Step 1.

Step 2.

Step 3.

Step 4.

Step 5.

Place battery switch to OFF position.

Disconnect lead 569A from heater switch.

Place battery switch to ON position.

Set multimeter to 50-volt range.

Connect multimeter negative lead to vehicle chassis ground and positive lead to lead

569A. Multimeter should indicate 12 to 13-volts.

a.

If battery voltage is not indicated, go to test 2.

b.

If battery voltage is indicated, replace defective heater switch (para. 3-107).

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