Download How to Test the Voltage Drop Between the Battery

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Vehicle
“How To”
Test Guide
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quality and use of this information is totally the responsibility of the end
user. Should any information contained in this CD prove to be defective,
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consequential damages.
Vested LLC does not warrant that the test setup and techniques
shown will meet the end uses requirements. Vested LLC does not
warrant that the test procedures are error free. All tests presented have
been performed by a Vested LLC representative with vehicle responding
results.
Vested LLC, its officers, agents, or representatives will in no way be
liable for any damages, including loss of profits, loss of savings, or other
consequential or incidental damages arising out of the use of the test
procedures contained in this CD.
The tests procedures presented on the CD have been performed
with the results shown. Vested LLC does not intend or imply that the
test procedures replace vehicle manufacturer's authorized or
recommended test procedures. Always check the information given
against that recommended by the manufacturer of the vehicle you are
working on.
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How To Use The Test Guide
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Use only the left and right mouse buttons as explained below.
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“Speaker Notes” for additional information. You may have to use the
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Now:
Lets go through an example of how to use the guide.
You will advance to a slide with further instructions, and come back here.
Left click the mouse on the blue button to access information on “Meters”.
X Meters.
When finished with the example,
left click your mouse to advance to the Master Index.
Vehicle “How to” Master Index
X
Meters.
X
Battery Testing.
X
Computer/Module Testing.
X
Continuity Testing and Ohmmeter Usage.
X
Current Path, Connections, and Switch Contact Testing.
X
Fuse, Fusible Link, and Circuit Breaker Testing.
X
Generator Testing.
X
Relay Testing.
X
Starter Testing.
X
Shared Current Path and Voltage Drop Testing.
X
Other Tests and Information.
(X buttons are active)
When finished, right click your mouse and left click on “End Show”.
Meters.
X
How Accurate is Your Test Meter? (X
buttons are active)
Understanding What a Voltmeter is Reading.
How to Set the DVOM Meter for Reading:
Open Circuit Voltage, Charging Voltage, or Source Voltage.
How to Set the DVOM Meter, Leads, and Probes for Reading:
The voltage drop between:
the battery positive (+) terminal and the input pin to any load on the vehicle.
How to Set the DVOM Meter, Leads, and Probes for Reading:
The voltage drop between:
the battery negative (-) terminal and the output pin or case ground from
any load on the vehicle.
How to Set the DVOM Meter, Leads, and Probes for Reading:
The amount of source voltage available to any load on
the vehicle.
How to Calibrate an Inductive Pick Up That Plugs into a Voltmeter.
How to Read a 100 millivolts per amp Inductive Pick up.
How to Make and Use a 10X Inductive Multiplier.
How to Extend Meter Leads When Testing a Long Distance From
the Battery.
Back
How Accurate is Your Test Meter?
Accuracy of:
Plus or minus 0.5% (.005%) is Acceptable
Plus or minus 0.1% (.001%) is Best
Check the owner’s manual for your meter under DC accuracy.
Lets compare meter readings of Best (0.1% accuracy) to Poor (1% accuracy)
If the actual charging voltage was 14.30V
and your meter had:
and another meter had:
Plus or minus 0.1% Accuracy (Best)
Plus or minus 1% Accuracy (Poor)
This meter could read:
This meter could read”
@ + .1% ------- 14.31V
@ + 1% -------- 14.44V
@ - .1% ------- 14.29V
@ - 1% -------- 14.15V
and be off actual by .014V
and be off actual by .143V
If the actual battery open circuit voltage was 12.66V
and your meter had:
and another meter had:
+ / - 0.1% Accuracy (Best)
+ / - 1% Accuracy (Poor)
This meter could read:
This meter could read:
@ + .1% ------- 12.67V
@ + 1% -------- 12.78V
@ - .1% ------- 12.65V
@ - 1% -------- 12.53V
and be off actual by .013V
and be off actual by .126V
Less than .050V (50mV) is a common acceptable voltage drop on a sensor or
computer ground. If your meter is off by 140mV, you will never find the problem.
Notes – Right click mouse, left click on speaker notes.
Back
Battery Testing
X How to Test the Voltage Drop Between the Battery (+) Post and Clamp.
How To Test For Voltage Drop Between The Battery (-) Post and Clamp.
How to Test the Open Circuit Voltage of the Battery.
How to Charge the Battery.
How to Do a Battery Load Test Using a VAT 40 or 45.
How To Do a Battery Load Test Without a Load Tester.
How to Find the Parasitic Drain on any Battery Using an Auxiliary Battery.
How to do a 3 - Minute Charge Test on a Battery.
How to Test the Voltage Drop Between the Battery (+) Terminal and the
Starter Motor Armature Lead.
How To Test the Voltage Drop Between:
The Battery Positive (+) Terminal and Fuses.
How To Test The Voltage Drop of a Battery Positive + Pigtail Wire .
How To Test Connectors and Connections of Positive Pigtail Wires.
How to test the voltage drop between the wire and the clamp material in a
battery positive (+) pigtail.
How to Test the Voltage Drop Between the Battery Negative (-) Terminal
and Where the Negative (-) Cable Attaches to the Frame or the
Block.
How to Test the Voltage Drop Between: the Battery Negative Cable
Conductor and its Connector.
How to Test the Voltage Drop Across a Suspect Negative Pigtail
Back
Cable or Wire Connector.
How to Test the Voltage Drop Between the Battery (+) Post and Clamp
Voltmeter set to read millivolts DC.
Set voltmeter to read millivolts. Post and
clamp can be tested for voltage drop as
shown. This important test cannot be
done on a side mount battery. Always
remove, clean, replace, and retighten both
(+) and (-) side mount cables as a starting
point to base system testing and good
troubleshooting.
Post Top & Side Mount Battery
Side mount battery
does not allow for
a voltage drop test
between the battery
mating surface and
the cable connector.
Electrolysis waiting to happen!
Copper
cable
connectors
Engine
EngineCranking
running
Reverse voltmeter lead positions
for testing the negative post
Alloy
coated
bolts
Lead
battery
surface
Notes
Back
Computer/Module Testing.
X
How to Test the Voltage Drop of Computer Voltage Feed Wires That
Can Be Back-probed.
How to Test the Voltage Drop of Computer Ground Wires That Can Be
Back-probed.
How to Load Test Computer Voltage Feed Wires.
How to Load Test Computer Ground Wires.
Back
How to Test the Voltage Drop of Computer Voltage Feed Wires
That Can Be Back-probed
Voltmeter set to read millivolts
.500V (500mV)
Maximum
Notes
Back
Continuity Testing and Ohmmeter Usage
X How to Test for Continuity with an Ohmmeter.
Cautions When Using an Ohmmeter.
How To Tell if Solid State Components are Affecting Ohmmeter
Resistance Readings.
Back
How to Test for Continuity with an Ohmmeter
1. Black lead to common (ground) input.
2. Red lead to volt / ohm input.
3. Set DVOM to Ohms.
4. Auto ranging meters are now set, non-auto ranging meters - set to lowest
ohms scale.
5. With meter set, and on, leads separated, note what your meter reads (this
could be “1" or “OL” or something else).
6. Touch the leads together, note what your meter reads (this could be 000.2,
000.4, or something else.
7. When the leads are touched together, this tells you that there is a
continuous path from the meter’s battery, through the leads, back
to the meter’s battery. There is “continuity”, or a “completed” circuit.
This type of “continuity” testing is useful to find and “open”, and a “short to ground” in a
piece of wire. If you touched one meter lead to each end of a piece of wire that you thought
was continuous, and your meter read what you saw in step 5 above, you have found an
“open”, and must replace the wire in order for the circuit to be complete.
Notes – Right click mouse, left click on speaker notes.
Back
Current Path, Connections, and Switch Contact Testing.
X
How to Test the Voltage Drop of Any Length of Wire.
How to Test for Available Voltage to a “Hot at All Times” Connection
How To Test For Available Voltage to a “Hot In Start Or Run” Connection
How to Load Test a “Hot at all Times Connection.
How to Load Test a “Hot in Start or Run” Connection.
How to Test Any Mechanical Switch Using an Ohmmeter.
How to do a Voltage Drop Test on Any Mechanical Switch.
How to Test the Voltage Drop of a “Suspect Wire Connector”.
Back
How to Test the Voltage Drop of Any Length of Wire
The wire to be tested must be in the circuit carrying current either to or from
the circuit load.
1. Set the voltmeter to read millivolts or on the lowest volt scale.
2. Put the voltmeter positive (+) probe on the end of the wire closest to the
battery.
3. Put the voltmeter negative lead on the other end of the wire.
4. Operate the circuit.
5. If the voltage drop is more than .100V (100mV), the wire, or connections are
bad.
6. If excessive, remove the wire at both ends and clean the connections, retest.
7. If still excessive, replace the wire.
Notes – Right click mouse, left click on speaker notes.
Back
Fuse, Fusible Link, and Circuit Breaker Testing.
X
How to Test the Voltage Drop Across a Fuse Connection.
How to use a Blown Fuse to Direct Your Troubleshooting.
How to Find a Short to Ground (that resulted in a blown fuse),
Using a Light Bulb Load.
How To Test Fusible Link Wire.
How To Quickly Test a Suspect Circuit Breaker.
Back
How to Test the Voltage Drop Across a Fuse Connection
Excess space between a fuse
tang and its female connector
can cause a voltage drop high
enough to affect the operation
of the circuit load.
“Wiggle” the fuse
during the test.
100mV Maximum
.100V Maximum
All circuits the fuse protects should be ON during this test if possible.
The higher the current flow, the greater the voltage drop. If a mechanical
fuse connection is loose enough, it can cause an intermittent.
Notes
Back
Generator Testing.
X How to Test the Generator Charging Voltage.
How to Test the Voltage Drop Between:
the Generator Output and the Battery Positive (+) Terminal.
How to Test the Voltage Drop Between:
the Battery Negative (-) Terminal and the Generator Housing.
How to Test the Voltage Drop Between:
the Generator Housing and the Block.
How to Test for Generator AC Riding on DC
How to Check For Bad Diodes in the Generator using the
“Diode Test Mode” of the DVOM.
How to Test for Shorted Diodes in the Generator Using the
“Micro Amp Range” of the DVOM.
How to Verify a Good Generator.
How to Test the Battery as a Possible Cause of Multiple
Generator Replacements.
Back
How to Test the Generator Charging Voltage
Set voltmeter to read volts DC.
Put voltmeter positive (+) probe
on battery (+) terminal.
Put voltmeter negative (-) probe
on battery (-) terminal.
Run the engine at 1500 RPM,
and turn on every load that can
be turned on – AC compressor,
blower motor, rear window
defogger, head lights, etc.
Let engine run for more than
1 minute after all loads are on.
Source voltage will be between
13.5 and 14.9 on most vehicles.
If above 15volts, this could be
caused by a faulty generator
regulator.
(Notes)
©
Back
Relay Testing
How to Deal With a “Suspect Relay”.
How to Troubleshoot a Relay Controlled Circuit.
Back
Starter Testing
X
How to Test the Cranking Voltage Available to the Starter Motor
How to Test the Voltage Drop Between:
the Battery (+) Terminal and the Starter Motor Armature Lead.
How to Test the Voltage Drop of a Starter Mounted or Remote
Mounted Solenoid.
How To Test the Voltage Drop Between:
Battery Negative (-) Terminal and the Starter Motor Housing.
How to Test the Voltage Drop Between:
the Starter Housing and the Block.
How to do a Starter Motor Amp Draw Test with a VAT 40 or 45.
How to do a Starter Motor Amperage Draw Test With a Load Tester
That Has a Voltmeter & Amp Meter, but No Inductive Pick Up.
How to do a Starter Motor Amperage Draw Test With an Inductive
Pick Up Plugged Into a Digital Voltmeter.
Back
How to Test the Cranking Voltage Available to the Starter Motor
Voltmeter negative (-) to
a clean post top or side
mount negative (-) bolt,
NOT on cable, or clamp.
Engine CRANKING
Should be within
2 ½ Volts of
Source Voltage
Voltmeter positive (+) to a
clean spot on the starter
motor armature lead, NOT
on solenoid nut, washer,
or stud.
The voltmeter is set to read volts DC.
This voltmeter will show the value of voltage that is available to the starter
motor while cranking. It does not show the actual voltage drop that is
Notes
occurring during cranking.
Back
Shared Current Path and Voltage Drop Testing.
X
How To Find Open Circuit, Charging, Or Source Voltage.
How To Find The Amount Of Source Voltage Available To Any
Load.
How To Find The Voltage Drop Between:
The Battery Positive Terminal And The Input Pin To Any
Load.
How To Find The Voltage Drop Between:
The Ground Side Of Any Load And The Battery Negative
Terminal.
How To Find The Voltage Drop Between:
Truck Bed And Cab Sheet Metal.
How To Find The Voltage Drop Between:
The Battery Negative (-) Terminal And The Bulkhead
Ground Strap.
How To Find The Voltage Drop Between:
The Bulkhead And The Block.
How To Find The Voltage Drop Between:
The Battery Negative (-) Terminal And A Battery
Negative (-) Pigtail Attached To Sheet Or Frame Metal.
Back
How To Find Open Circuit, Charging, Or Source Voltage
This meter probe set up shows the value of the battery’s open circuit
voltage, some times referred to as “source voltage” when the engine is off.
It also shows the value of the battery’s charging voltage, sometimes also
referred to as “source voltage” when the engine is running.
Back
Other Tests and Information.
X How to Stop Electrical Switch Pop “Noise” in a Radio.
How a Voltage Drop Can Cause Ring Gear Damage.
How To Find the Percent of Alcohol in Gasoline.
How to Check for Water in Brake Fluid Using a Voltage Drop Test.
How to Check Acid Content In Coolant With a Voltage Drop Test.
How to Test a Rear Window Defogger Using a Test Light.
How to Test a Rear Window Defogger using a Voltmeter.
How to Test Thermistor Temperature Sensors.
Battery Drain Times When Components are Left On.
Wire Sizes, Diameter, Ohms/1000Ft. and Rated Continuous Amperage
Observed wire sizes used on a 2007 C/K GMC.
How DC “Motor Drag” Can Affect Voltage Drop.
How DC Motor In-Rush Current Can Affect Voltage Drop.
Precautions to Observe Whenever a Vehicle Component is Unplugged.
When the Voltage Drop Is Still Excessive after Repair, Then What? Back
How to Stop Electrical Switch Pop “Noise” in a Radio
Switches and motors can cause electrical
“noise” in a radio.
1
1’st capacitor: Wire to voltage feed side
of the switch. Case to load
side.
Electrons jumping air gaps when switch or
relay contacts open can sometimes cause
a “popping” noise in a radio. The drawings show
three progressive steps for placing capacitors
to eliminate this problem.
There is space between a motor brush and its’
contact surface that allows an air gap. If the
brush “bounces” the air gap is increases. When
ever an electron travels in “open air” its will emit
radio frequency interference waves. This we hear
as static in our radio.
2
2’nd capacitor: Wire to same location.
Case to ground.
3
3’rd capacitor: Wires to load side.
Case to ground.
Condensers (capacitors) can also be located
“across” or in parallel with generator brushes to
slip rings and brushes to armature in motors.
If a condenser is placed in parallel across the
brush / slip ring, or brush / armature , the
electron will take a path of lease resistance and
go into the capacitor rather than leap the air gap.
Doing this, it will emit less radio frequency
interference.
Radio Shack part #272-126 or #272-131
capacitors.
Notes
Next
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