TM 9-2330-390-14&P
Table 4-2. Unit Troubleshooting (Con’t).
MALFUNCTION
TEST OR INSPECTION
CORRECTIVE ACTION
Step 7.
If malfunction persists during tandem towing, problem may be with booster relay valve of front
dolly set. A malfunctioning booster relay valve will not adequately amplify the service brake signal
to rear dolly set.
Replace damaged booster relay valve (see paragraph 4-63 or 4-67).
7.
SLOW APPLICATION OR SLOW RELEASE OF BRAKES.
l DO NOT disconnect air lines and fittings while dolly set airbrake system is
pressurized. Intervehicular air lines must be disconnected and air reservoirs drained
before air lines and fittings are disconnected. A line or fitting disconnected under
pressure may explode with great force and cause serious injury to personnel.
l Wear eye protection when working with compressed air to avoid serious eye injury.
NOTE
Refer to airbrake system schematics for assistance (see paragraph 4-74).
Step 1.
Perform airbrake system leakage check (see paragraph 4-23). Check all air hoses between
intervehicular service air hose and airbrake chambers for leaks or other damage.
Replace damaged air lines (see paragraph 4-72 or 4-73).
Step 2.
With dolly set airbrake system fully pressurized, check for defective relay emergency valve (front
dolly) or full function valve (rear dolly). Apply service brakes, then release. Listen for sound of air
releasing from exhaust port on underside of valve. After an initial release of air, there should be no
more leakage.
Replace defective relay emergency valve (see paragraph 4-62) or full function valve (see
paragraph 4-66).
Step 3.
Check for properly adjusted brakes (see paragraph 4-59).
Perform minor brake adjustment (see paragraph 4-59).
Step 4.
If brakes do not adjust properly, remove hub and brakedrum (see paragraph 4-75). Check for
weak or broken brakeshoe return springs (see paragraph 4-57).
Replace damaged brakeshoe return springs and any other damaged components (see
paragraph 4-57).
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