Section IV. TROUBLESHOOTING
2-10. INTRODUCTION TO LOGIC TREE TROUBLESHOOTING
This section contains step-by-step procedures for identifying, locating, isolating, and repairing equipment malfunctions.
This manual cannot list all malfunctions that may occur, nor all tests or inspections and corrective actions. If a
malfunction is not listed or is not corrected by listed corrective actions, notify your supervisor.
2-11. TROUBLESHOOTING INSTRUCTIONS
Page Layout. Troubleshooting procedures are divided into logic tree pages and test pages.
(1) A logic tree page is always a left-hand page, facing the test page on the right. The logic tree page provides
the sequence of steps required to isolate a fault to a failed component. All critical information for decision
making is on the left-hand page. Each logic tree page contains the following information:
(a) INITIAL SETUP - This box is located only on the first logic tree page of a fault. INITIAL SETUP lists
tools, materials, references, personnel, and equipment needed to troubleshoot the fault.
(b) KNOWN INFO - This box is located in the top left-hand column. KNOWN INFO lists conditions and
information that will eliminate specific components as the cause of the fault.
(c) POSSIBLE PROBLEMS - This box is located directly below KNOWN INFO. All of the system
components that could cause a fault are listed in the POSSIBLE PROBLEMS box. The first component
listed in the POSSIBLE PROBLEMS box is the one that will be tested at that step in the logic
sequence. When one of the components is tested and found to be operational, it is entered at the
bottom of the KNOWN INFO box as OK.
(d) QUESTION - Each question, located in the middle column, refers to the first possible problem listed
in POSSIBLE PROBLEMS. If the answer to the question is YES, proceed to the next step. If the
answer is NO, follow the NO arrow to obtain directions for correcting the problem. If the step contains
a WARNING or CAUTION message, a small shadow box is printed above the question. Text for
WARNINGs or CAUTIONs is on the following right-hand page.
(e) TEST OPTIONS - This box is located in the top right-hand column. TEST OPTIONS lists tests available
for testing parts suspected of failing. When the TEST OPTION is a VOLTAGE TEST, the voltage
values listed are nominal values for a 12/24 VDC system. Some variation from these values should
be expected. When the TEST OPTION is a CONTINUITY TEST, the expected reading is one of low
resistance. If high resistance is noted, further testing should be performed to determine the cause.
REASON FOR QUESTION - This box is located directly below TEST OPTIONS. It explains the purpose
for the question in the middle column.
(2) A test page is always a right-hand page, facing the logic tree page on the left. The test provides detailed
instructions for testing the first component listed in the POSSIBLE PROBLEMS box. This test will also
provide an answer for the question in the middle column. Note the arrow connecting the test on the right-
hand page to the REASON FOR QUESTION. When possible, illustrations are included to provide visual
details. Notes contain additional information for testing.