TM 55-4920-414-13&P
Table 4-3. Troubleshooting - Test Fixture
MALFUNCTION
TEST OR INSPECTION
CORRECTIVE ACTION
1.
HYDRAULIC FLUID LEAKAGE.
Step 1.
Step 2.
Step 3.
Step 4.
Step 5.
Step 6.
Step 7.
Place Test Box POWER DC switch ON.
Set hydraulic test stand output pressure control to zero, then turn on hydraulic test stand and set fluid
pressure for 2000 psi at 2 gpm.
a. If quick-disconnect couplings leak, replace coupling, paragraphs 4-18 and 4-19.
b. If thermal switch leaks, replace thermal switch, paragraph 4-16.
Increase hydraulic test stand fluid pressure to 3000 psi.
a. Replace any leaking item.
Place Test Box TRIM, SAS, and BOOST switches ON. TRIM pressure gage shall indicate between 950 and
1050 psi. SAS PRESS ON indicator shall light. BOOST pressure gage shall indicate between 2500 and
3050 psi.
a. If TRIM pressure gage reading is zero, replace TRIM SHUTOFF VALVE, paragraph 4-13.
b. If TRIM pressure gage reading is out of tolerance, replace pressure reducer, paragraph 4-14.
c. If BOOST pressure gage reading is incorrect, replace BOOST SHUT-OFF three-way valve, paragraph 4-13.
d. If SAS PRESS ON indicator does not light, replace SAS pressure switch, paragraph 4-15.
Place Test Box SAS switch OFF. TRIM pressure gage shall indicate between 950 and 1050 psi. SAS PRESS
OFF indicator shall light. BOOST pressure gage shall indicate between 2500 and 3050 psi.
a. If SAS PRESS OFF indicator does not light, replace SAS pressure switch, paragraph 4-15.
Place Test Box BOOST switch OFF. TRIM pressure gage shall indicate between 950 and 1050 psi. SAS
PRESS OFF indicator shall light. BOOST pressure gage shall indicate zero.
a. If BOOST pressure gage reading is incorrect, replace BOOST SHUT-OFF three-way valve, paragraph 4-13.
Place Test Box TRIM switch OFF, SAS switch ON, and BOOST switch ON, TRIM pressure gage shall
. . .
indicate zero. SAS PRESS ON indicator shall light. BOOST pressure gage shall indicate between 2500
and 3050 psi.
a. If TRIM pressure gage does not indicate zero, replace TRIM SHUT-OFF VALVE, paragraph 4-13.
2.
SAS PRESS ON AND SAS PRESS OFF INDICATORS RESPOND TO INCORRECT PRESSURES.
Step 1.
Step 2.
Step 3.
Step 4.
Step 5.
Step 6.
Step 7.
Step 8.
Place Test Box TRIM switch OFF, SAS switch ON, and BOOST switch OFF.
Reduce hydraulic test stand pressure to a value between 1900 and 2050 psi. SAS PRESS OFF indicator
shall light green.
a. If SAS PRESS OFF indicator does not light, replace SAS pressure switch, paragraph 4-15.
Slowly increase hydraulic test stand pressure toward 3000 psi until SAS PRESS ON indicator lights green.
Hydraulic test stand pressure gage should not indicate more than 2400 psi.
a. If SAS PRESS ON indicator does not light, replace SAS pressure switch, paragraph 4-15.
Reduce pressure to zero psi and shut off hydraulic test stand.
Remove hydraulic lines from Test Fixture.
Remove pressure gages from Test Fixture.
Place Test Box POWER DC switch OFF.
Remove and stow all test and power cables.
4 -7
