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 1264 of 1313
CONTROL PANEL LIGHTS WORK, SYSTEM FAILS TO INFLATE OR DEFLATE - Continued
STEP
10.
IS THERE NO CONTINUITY BETWEEN PRESSURE SWITCH PINS A AND B WHEN AIR SYSTEM IS
BELOW NORMAL OPERATING PRESSURE?
a.
Refer to point to point schematics.
T0426DAA
PRESSURE
SWITCH
Figure 9.
Pressure Switch.
b.
Connect multimeter red lead to pressure switch at pin A.
c.
Connect multimeter black lead to pressure switch at pin B.
d.
Shut off air supply or engine.
e.
Drain secondary tank until air pressure gauge indicates less than 80 psi.
f.
Pressure switch should open.
g.
Meter reading should be greater than 90 ohms.
CONDITION/INDICATION
IS THERE CONTINUITY BETWEEN PRESSURE SWITCH PINS A AND B WHEN AIR SYSTEM IS BELOW
NORMAL OPERATING PRESSURE?
DECISION
YES - Go to Step (11) to verify problem is solved.
NO - Replace pressure switch (Volume 2, WP
0324). Go to Step (11) to verify problem is solved.
TM 9-2320-272-23-1
0149
0149-11
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