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 344 of 481

TM 9-2320-272-10

2-235

(3)

Press PRESS-TO-TEST button (7) on engine coolant heater control box

(5) to check operation of circuit. Observe that indicator lamp (7) illuminates.

(4)

Set HI-LO switch (6) on engine coolant heater control box (5) to

HI or LO.

NOTE

Select HI position if engine is cold. Switch will automatically

change to LO 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).

(5)

Hold RUN-OFF-START switch (8) on engine coolant heater control box

(5) in START position until indicator lamp (7) illuminates.

NOTE

Heater will not operate if switch is moved to RUN position

before indicator lamp illuminates.

(6)

Move switch (8) to RUN, without hesitating at OFF, as soon as indicator

lamp (7) illuminates.

2-45. ENGINE COOLANT HEATER KIT (Contd)