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9.4 V
60° F /16° C
9.2 V
50° F /10° C
9.0 V
40° F / 4° C
8.8 V
30° F / –1° C
8.6 V
20° F / –7° C
NOTE: Battery temperature can be checked
with the Meter temperature function.
Voltage Drop Test
Voltage drop tests measure the amount of
voltage expended to overcome resistance
(an opposing force created by a circuit
or component to the flow of electrical
current); the lower the voltage drop
reading, the less resistance there is in the
circuit being tested.
The Meter has a very useful Fix Hold
function for measuring voltage drops
on many different components and
connections.
Measuring the voltage drop across the
connections and components in the starter
circuit, while cranking the engine with
the ignition or fuel system disabled to
prevent starting, will indicate if there is any
resistance in a starter circuit.
To measure voltage drop, current must be
flowing in the circuit, and both voltage
test probes must be connected on the same
side of the circuit.
Voltage drop can also be determined
from available voltage readings by noting
the difference between each successive
reading.
Always refer to the vehicle manufacturer’s
specification for voltage drop information.
If the voltage drop specification is not
available, refer to the following list to
determine the circuit’s maximum allowable
voltage drop.
Typical maximum allowable voltage drop
values for 12 volt systems are as follows:
Battery cable length up to 3 feet
0.1V
Battery cable length over 3 feet
0.2V
Magnetic switches
0.3V
Solenoid switches
0.2V
Mechanical switches
0.1V
Battery cable connectors
0.05V
Connections
0.0V
NOTE: Do not use the allowable voltage
drop values listed above on circuits that use
aluminum cables.
Maximum voltage drop, normally, should
not be more than 0.1V per wire, ground,
connection, switch or solenoid. Thus, with
the negative test probe connected to the
negative battery post and the positive
test probe connected to the starter drive
housing frame, total voltage drop should
not exceed 0.4 volts.
If the voltage drop reading is within
the allowable maximum voltage drop
specification, the circuits resistance is
acceptable.
If the voltage drop reading exceeds the
maximum allowable voltage drop, the
point of excessive resistance can be located
by checking the voltage reading at each
connection and cable end. When a sharp
decrease in voltage drop is observed, the
cause of the excessive resistance will be
located between that test point and the
previous test point.
Summary of Contents for UD226
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