TM-9-2320-272-10

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

TECHNICAL MANUAL; OPERATOR'S MANUAL

SEPTEMBER 2004

CHANGE 2

TM-9-2320-272-10 - Page 367 of 481

TM 9-2320-272-10

3-18

MALFUNCTION

TEST OR INSPECTION

CORRECTIVE ACTION

Table 3-1. Troubleshooting (Contd).

46. ENGINE COOLANT HEATER FAILS TO START WHEN RUN-OFF-START SWITCH

IS HELD IN START POSITION.

WARNING

Exhaust gases can kill. Do not operate engine coolant

heater in closed area occupied by personnel. Such

action will result in injury or death.

CAUTION

Do not operate engine coolant heater and personnel heater

at the same time. Damage to equipment may result.

NOTE

• Select HI position if engine is cold. Select LOW position if

engine is already well heated. Switch will automatically

change to LOW position when coolant temperature exceeds

195°F (91°C). Switch will automatically change to HI

position when coolant temperature drops below 120°F

(49°C).

• Heater will not operate if RUN-OFF-START switch is

moved to RUN position before indicator lamp illuminates.

Step 1. Press PRESS-TO-TEST button on heater control box to check

operation of circuit.

If indicator lamp does not illuminate, notify unit maintenance.

Step 2. Check fuel level on fuel gauge.

Fill fuel tank(s) if necessary.

Step 3. Check to see if electric fuel pump shutoff valve located near air

cleaner assembly is closed (para. 2-45).

If closed, open fuel shutoff valve.

47. HEATER FAILS TO CONTINUE BURNING.

Check fuel level on fuel gauge.

Fill fuel tank(s) if necessary.