TM-9-2320-272-23-1

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

TECHNICAL MANUAL; FIELD MAINTENANCE MANUAL; VOLUME 1 OF 5

SEPTEMBER 2012

TM-9-2320-272-23-1 - Page 970 of 1313

HEATER WILL NOT OPERATE IN LOW OR HIGH POSITION - Continued

c.

Disconnect circuit 400 wire from heater blower motor.

d.

Place battery switch to ON position.

e.

Place heater switch to HIGH speed position.

f.

Set up multimeter to measure VDC.

g.

Connect multimeter red lead to the disconnected circuit 400 wire. Refer to point to point schematics.

h.

Connect multimeter black lead to vehicle chassis ground.

NOTE

If voltage is present, heater blower motor is faulty.

i.

Meter reading should be greater than 18 VDC.

CONDITION/INDICATION

IS HEATER BLOWER MOTOR IN GOOD OPERATING CONDITION?

DECISION

NO - Replace heater blower motor (Volume 4, WP

0747). Go to Step (3) to verify problem is solved.

YES - Go to Step (2).

TM 9-2320-272-23-1

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