STAR Service News Missed an issue? - Toyota Parts & Service

TOYOTA TECHNICAL
• Connect the voltmeter leads
in parallel with the circuit element
to be tested (red lead closest to
the battery. Connect red/positive
fi rst. The black lead is then connected
to ground).
• Read the measurement on
the DMM display (note polarity
— the meter leads are most likely
reversed if the DMM display indicates
negative polarity; it could
also indicate a fault in the circuit).
VOLTAGE DROP TESTS
To check for a charging prob-
Battery positive circuit, meter connected
to measure voltage drop.
Magnetic switch, meter connected to measure
voltage drop.
lem, use a DMM to perform a
voltage drop test on the positive
side of the battery. Connect the
red meter lead to Terminal B on
the alternator. Connect the black
meter lead to the positive battery
terminal.
Start the engine and adjust idle
speed to 2,000 rpm. Note the
voltage reading. The voltage drop
should be less than 0.2V. If the
reading is higher, look for poor
connections at the alternator and
at the battery. Also look for damaged
or corroded wires.
Test for voltage drop on the
ground side of the battery. Keep
the engine running at 2,000 rpm.
Connect the black meter lead to
the negative battery terminal.
Connect the red meter lead to
the alternator frame and note the
voltage reading. The voltage drop
should be less than 0.2V. If the
reading is higher, look for poor
connections between the battery
and ground, and from the alternator
frame to ground.
Also check for a damaged or
corroded battery ground cable.
Battery negative circuit, meter connected
to measure voltage drop.
Starter control circuit, voltage drop testing
can fi nd excessive resistance.
10 STAR Service News
Spring 2010