TM 5-3810-307-24-1-2
5b. ANTI-TWO BLOCK PROBLEM (DOUBLE SWITCH)
PROBLEM: Function of Anti-Two Block System is faulty.
START
Check to see whether or not crane is in two-block condition.
Correct?
NO
Lower hook down into safe position.
YES
Turn power off or disconnect blue wire from X1:35 on connection board in central unit.
Refer to Drawings 2, 3, 14 in Section 10.
Remove length cable core wire from terminal 1 in Boom Nose Junction Box.
Measure the resistance at the boom nose junction box between terminals 2 and 3 with
ohmmeter. This checks the function of the Secondary (Right) anti-two block switch.
Secondary (Right) anti-two block switch closed = 4700 Ohms 500 Ohms (weight installed)
Secondary (Right) anti-two block switch open => 1 Megaohm (weight removed)
Refer to Drawing 22 in Section 10.
Correct?
NO
Replace Secondary (Right)
anti-two block switch.
YES
Measure the resistance of the primary anti-two block switch between
1 and 2 with ohmmeter. This checks the function of the primary (left) anti-two block switch.
Primary (Left) anti-two block switch closed =< 100 Ohms (weight installed)
Primary (Left) anti-two block switch open => 1 Megaohm (weight removed).
Refer to Drawing 22 in Section 10.
Replace length cable core wire to terminal 1 in boom nose junction box.
Correct?
NO
Replace Primary (Left)
anti-two block switch.
YES
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