Voltage Drops - Actron AutoTroubleShooter Operating Instructions Manual

Voltage Drops

This test measures the voltage drop across
wires, switches, cables, solenoids, and
connections. With this test you can find
excessive resistance in the starter system.
This resistance restricts the amount of
current that reaches the starter motor
resulting in low battery load voltage and a
slow cranking engine at starting.
Test Procedure (see Fig. 22):
1. Disable ignition system so vehicle
won't start.
Disconnect the primary of the igni-
tion coil or the distributor pick-up coil
or the cam/crank sensor to disable
the ignition system. Refer to vehicle
s e r v i c e m a n u a l f o r d i s a b l i n g
procedure.
2. Insert BLACK test lead into COM
test lead jack.
3. I n s e r t R E D t e s t l e a d i n t o
4. Connect test leads.
Refer to Typical Cranking Voltage
Loss Circuit (Fig. 22).
• Connect RED and BLACK test leads
alternately between 1 & 2, 2 & 3, 4 &
5, 5 & 6, 6 & 7, 7 & 9, 8 & 9, and 8 &
10.
5. Turn multimeter rotary switch to
200mV DC range.
Fig. 22 Typical Cranking Voltage
Loss Circuit
This is a representative sample of
one type of cranking circuit. Your
vehicle may use a different circuit
with different components or
locations. Consult your vehicle
service manual.
10
Starter
test lead jack.
1
If multimeter overranges, turn multim-
eter rotary switch to the 2V DC range.
(See Setting the Range on page 6)
6. Crank engine until steady reading
is on display.
• Record results at each point as
displayed on multimeter.
• Repeat Step 4 & 5 until all points
are checked.
7. Test Results –
Estimated Voltage Drop of Starter
Circuit Components
Component
Switches
Wire or Cable
Ground
Battery Cable
Connectors
Connections
• Compare voltage readings in Step
6 with above chart.
• If any voltages read high, inspect com-
ponent and connection for defects.
• If defects are found, service as
necessary.
Solenoid
9 8
6
7
5
4
2
18
Voltage
300mV
200mV
100mV
50mV
0.0V
Red
5
3
3
6 8
7
9
Black
4
2