MAINTENANCE OF M939 SERIES VEHICLES - OD1661 - LESSON 1/TASK 2
troubleshooting step 2 to test the low air pressure switches and
circuits.
Step 2.
The procedures in this step are illustrated in figure 26.
To begin this step, SSG Gilbert disconnects the circuit 578 wire from
pressure switch A. Since the buzzer sounded, SSG Gilbert reconnects
the circuit 578 wire to pressure switch A and proceeds.
FIGURE 26.
TEST PROCEDURES FOR PRESSURE
SWITCHES A AND B.
He now disconnects the circuit 578A wire from pressure switch A, and
connects a jumper wire from the vehicle chassis ground to the circuit
578A terminal on pressure switch A. Again the buzzer sounds, so SSG
Gilbert reconnects the circuit 578A wire and proceeds.
Step 3. SSG Gilbert disconnects circuit 57 wire from pressure switch
B and the buzzer sounds.
This indicates that pressure switch B is
defective and needs to be replaced.
The procedures for replacing
pressure switch B are contained in paragraph 4-49 of TM 9-2320-272-
20-1.
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