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Chapter 7: Cable Drop Test
If the test results for the starter or charging systems indicate that there may be a problem, you may want
to perform the Cable Drop Test to determine if it is due to worn cables or bad connections between the
battery and the alternator or starter. Worn cables or bad connections create higher resistance, which
causes a drop across the circuit. The voltage drop reduces current carrying capability that displays the
same symptoms as a weak alternator or starter and causes premature battery failure.
There’s no need to run the engine. The Cable Drop Test uses Midtronics’ conductance technology to
send a signal through the circuit at the component under test. The EXP then simultaneously calculates
voltage drop on the positive (+) and negative (–) sides of any circuit as well as the total voltage drop.
The amperage range for each of the four tests is 0 to 1000 A. When you change the setting from the
factory defaults, the EXP will store your setting in memory for your next test.
There are three preset tests:
• BATTERY GROUND
• STARTER CIRCUIT
• ALTERNATOR CIRCUIT
A fourth test, OTHER CIRCUIT, tests other grounds and circuits against your specied amperage
capacity.
The test requires two test lead connections, as shown in Figure 17:
• Battery test leads at the component’s output lead (the B+ or output screw on the
alternator) and the component’s housing as ground
• DMM test leads at the battery terminals
NOTE: The test requires a complete circuit. If you’re testing a system with a remote
solenoid, you can test from the battery to the solenoid, but not from the battery to the
starter.
R
Battery
Battery Test Lead
DMM Test Lead
Component
Under
Test
1
R
2
+
–
Red Red
Black Black
Figure 17: Connections for the Cable Drop Test
Chapter 7: Cable Drop Test
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