DIRECT SUPPORT TROUBLESHOOTING INTRODUCTION
This chapter contains step-by-step procedures for identifying, locating, isolating, and repairing the HET Tractor A/C
system equipment malfunctions.
This technical bulletin 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 the supervisor.
Page Layout. Troubleshooting procedures are divided into logic tree pages and test pages.
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 compo-
nent 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 bot-
tom 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 con-
tains a warning or caution message, a small shadow box is printed above the question. Text for warn-
ings and 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.
(f) REASON FOR QUESTION This box is located directly below TEST OPTIONS. It explains the
purpose for the question in the middle column.
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. Warnings, cautions, and notes contain additional information for testing.
How to Begin Troubleshooting.
Determine the symptom or condition that indicates a problem or failure. Troubleshooting is divided into
Open the technical bulletin flat so both the left-hand and right-hand pages are displayed before you. The
information on both pages is important to resolve the problem or failure. However, the experienced techni-
cian can follow the left-hand page instructions and refer to the right-hand page when necessary.
Follow the Diagnostic Procedure. Answer question no. 1 on the left-hand page and follow the YES or NO
path to either the remedy or the next question. If necessary, look on the right-hand page for test instruc-
tions and illustrations.
Observe warnings, cautions, and notes. The formatting and symbols used in this manual for warnings, cau-
tions, and notes are as follows: