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 1292 of 1313
SLOW AIR RECOVERY OR OCCASIONAL LOW AIR WARNING DURING BRAKING - Continued
STEP
4.
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.
T0473DAA
WIRE HARNESS
PRESSURE
SWITCH
LEAD
PRESSURE
SWITCH
A
B
Figure 4.
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 read open (no continuity).
g.
Meter reading should be greater than 90 ohms.
CONDITION/INDICATION
IS THERE NO CONTINUITY BETWEEN PRESSURE SWITCH PINS A AND B WHEN AIR SYSTEM IS BELOW
NORMAL OPERATING PRESSURE?
DECISION
YES - Go to Step (5).
NO - Replace pressure switch (Volume 2, WP
0324). Go to Step (6) to verify problem is solved.
TM 9-2320-272-23-1
0153
0153-7
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