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 957 of 1313
HEATER WILL NOT OPERATE WITH SWITCH IN LOW POSITION (HIGH POSITION OPERATION NORMAL) -
Continued
STEP
1.
DOES CIRCUIT 569A WIRE SUPPLY PROPER VOLTAGE TO HEATER SWITCH?
a.
Check for 12 or 13 volts at circuit 569A wire.
b.
Place battery switch to OFF position.
T0125DAA
400
5C
569A
Figure 1.
Heater Switch Wiring.
c.
Disconnect circuit 569A wire from heater switch.
d.
Place battery switch to ON position.
e.
Set up multimeter to measure VDC.
f.
Connect multimeter red lead to the disconnected end of circuit 569A wire. Refer to point to point
schematics.
g.
Connect multimeter black lead to vehicle chassis ground.
h.
Meter reading should be 12 VDC or greater.
CONDITION/INDICATION
DOES CIRCUIT 569A WIRE SUPPLY PROPER VOLTAGE TO HEATER SWITCH?
DECISION
NO - Go to Step (2).
YES - Replace heater switch (Volume 2, WP
0307). Go to Step (5) to verify problem is solved.
TM 9-2320-272-23-1
0114
0114-2
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