Electrical System Troubleshooting; Four Basic Checking Items For Electrical Diagnosis - Kubota KX080-3 Workshop Manual

WSM KX080-3 Service
A.Troubleshooting
a. General guideline
(1) How to diagnose
The most important point in troubleshooting is to determine "Probable Causes". Once the probable
causes are determined, parts to be checked can be limited to those associated with such probable
causes. Therefore, unnecessary checks can be eliminated. The determination of the probable causes
must be based on a theory and be supported by facts and must not be based on intuition only.
TROUBLESHOOTING STEPS
If an attempt is made to solve a problem without going through correct steps for troubleshooting, the
problem symptoms could become more complicated, resulting in failure to determine the causes cor-
rectly and making incorrect repairs.The four steps below should be followed in troubleshooting.
Observation of Problem
1 Symptoms
Determination of Probable
2 Causes
Checking of Parts Associated
3 with Probable Causes and
Determination of Faulty Parts.
Repair and Confirmation
4

FOUR BASIC CHECKING ITEMS FOR ELECTRICAL DIAGNOSIS

This manual contains the cable diagrams as well as the individual circuit drawings, operational expla-
nations, and troubleshooting hints for each component required to facilitate the task of troubleshoot-
ing. The information is compiled in the following manner:
1. "Power source"
Is the supply voltage as specified? (Battery voltage at 12 V or microcomputer output at 5 V)
If not specified, the system fails to work.
2. "Continuity"
Is there continuity along the specified lines and wire harnesses? Are the system's resistance values
as specified?
If not specified, no current flows.
3. "Earth"
Is the system completely grounded?
If not grounded as specified, the electrical circuitry fails to function well.
4. "Insulation"
Are the system's insulation resistances as specified?
If an electric leak occurs, the current gets out of spec and the electrical devices malfunction.
Observe the symptom carefully. Check if there are also
other problems.
In determining the probable causes, it is necessary to
check the wiring diagram to understand the circuit as a sys-
tem. Knowledge of switches, relays and other parts is nec-
essary for accurate determination. The causes of similar
problems in the past must be taken into account.
Troubleshooting is carried out by making step by step
checks until the true cause is found. Always go through the
procedures considering what check is to be made where
for the best results.
After the problems are corrected, be sure to check that the
system operates correctly. Also check that new problems
have not been caused by the repair.
V-S-3
Electrical system