Technician’s Version

“How To Test” The Vehicle

Base Systemof

Shared Current Pathsfor

Voltage Drop

Left click the mouse to advance.

Demo

The full version of this CD contains the following:

63 slides on "Understanding Voltage Drop and Shared Current Paths“

How Connections Affect Voltage Drop. 3 page word doc.

27 slides on "Meters", Set Up and Probe Placement When Testing for Voltage and Voltage Drop.

General Rules for Allowable Voltage Drop in Vehicle Circuits. 5 page word doc.

53 slides on "How to Do Voltage Drop Testing".

52 slides on "How to Test Vehicle Shared Current Paths for Voltage Drop"

All slide programs are in Power Point Show. You must have power point to view them.

This demo reviews: "How to Test Vehicle Shared Current Paths for Voltage Drop"

Left click the mouse to advance.

About the material on this CD

The power point and word documents contained on this CD are provided without expressed or implied warranty. The entire risk as to the 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, the end user assumes the entire cost of any and all incidental and 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. Use Left Mouse Button to Advance

How to use this Vehicle Testing Guide

1. When you see “notes” at the bottom right of a slide, right click your mouse then left click on “speaker notes” for additional information.

Try this now. Right click on the mouse. Now left click on “speaker notes”. 2. Never use the “Enter” key on your computer. If you inadvertently hit the enter key or left mouse button, just right click the mouse button, and left click on “previous” to take you back. 3. Only use the left mouse button to push only the “action buttons”.

4. Use the “back” button to return to an index.

5. To begin viewing the testing guide, push this action button

How To Test the Vehicle Base System of Shared Current Paths

Always Begin at the Battery.

Starter Motor Voltage Feed Side Tests.

Starter Motor Ground Side Tests.

Battery Positive (+) Cable Pigtail Wire Tests.

Battery Negative (-) Cable Pigtail Wire Tests.

Ground Straps Not Attached to Negative Battery cable - Tests.

Generator Voltage Feed Wire Tests

Generator Ground Tests.

Other Generator Tests.

X

X

X

X

X

X

X

X

X

Battery Tests

First, Do an open circuit voltage (OCV) test.

If OCV is too low, Charge the battery. Do a load test with a VAT 40 or 45 if needed.

Do a load test without a load tester if needed.

Do a 3 - minute charge test if you suspect the battery is sulfated.

Do a parasitic drain test if needed.

With all necessary battery tests finished, go to: Tests for Voltage Drop in the Starter Motor Voltage Feed Side. ©

How?

How?

How?

How?

How?

How?

Back toIndex

or if you don’t have a load tester:

X

X

Battery voltage with the engine OFF is called “open circuit” voltage. There is no significant load (only parasitic) on the battery. This test is a sign of the battery’s “health”. The chart to the right shows what “state of charge” a battery is in based on the open circuit voltage tested. The minimum voltage you should accept as a base line for doing further testing is 12.5V. This value tells you that the battery is over 75% charged. If you find less than 12.5V, even 12.49V, trickle charge the battery overnight, if possible. If you don’t have time, fast charge for at least 4 hours at 5 to 10 amps. Only after being assured that the battery open circuit voltage is 12.5 or above can you test with accuracy to see if the battery is good or bad.

1. Key is OFF.2. Meter set to read volts DC.3. Positive (+) probe to battery (+)4. Negative (-) probe to battery (-)

Open Circuit Voltage Testtells Battery

state of charge 12.6V = 100% 12.5V = 75% 12.3V = 50% 12.1V = 25%

How to Test the Open Circuit Voltage of the Battery

Back©Notes

Do the “all-inclusive” voltage drop test. or, Test the cranking voltage , the “available voltage” to

the starter motor.If excessive:

Test solenoid contacts if needed.

Test connectors and connections if needed. Don’t overlook excessive amperage draw as the

cause of higher than normal voltage drops in the starter motor circuit.

When all necessary starter motor voltage feed side

tests are complete, go to:

How to Test for Voltage Drop in the Starter Motor Voltage Feed Side Current Path

How?

How?

How?

How?

How?

Back toIndexHow to Test the Starter Motor Ground.©

X

X

The voltmeter is set up to read volts DC.This voltmeter lead setup tells you exactly how much voltage is dropping between the battery positive (+) terminal and the starter motor armature while CRANKING. This “all-inclusive” test checks the following for voltage drop: connection between the positive (+) battery terminal and the clamp, connection between the copper in the cable and the clamp, any connections in the current path to the starter armature; this could includea solenoid. Maximum allowable is 2 1/2 Volts. ©

(-) Meter Probe

Voltmeter positive (+) probe to cleanpost top or side mount positive (+) nut – NOT on cable or clamp.

Voltmeter negative (-) probe to the starter motor armature lead – NOT on nut, washer, or solenoid stud.

negative (-)probe to starter motor armaturelead.

How to Test for the Actual Voltage Drop Between the Battery (+) Terminal and the Starter Motor Armature Lead

Back(Notes)

Do the “all-inclusive” voltage drop test. If excessive: Test between the starter motor housing and the

block if needed.

Test between the battery negative terminal and the frame or block where the negative cable is attached if needed.

Test between the negative cable and the battery post if needed.

Test between the negative cable and its connector if needed.Once all starter ground testing is complete, go to:

How to Test for Voltage Drop in a Battery Positive Cable Pigtail Wire. ©

How to Test for Voltage Drop in the Starter Motor Ground Side Current Path How?

How?

How?

How?

How?

Back toIndex

X

X

Voltmeter (-) probe or clip to a cleanpost or side mount bolt,NOT on cable or clamp

Set Voltmeter to read millivolts or on the lowest volt

setting.

Engine must beCRANKING

while meter is read.Disable engine fromstarting – this is a test of the starter

ground while cranking.

Voltmeter (+) probe to a clean spot on the

starter housing, NOT on block, exhaust

manifold, etc. ©

How To Test the Voltage Drop Between:Battery Negative (-) Terminal and the Starter Motor Housing

An “All-inclusive” Test of the Starter Motor’s Ground

Back

(Notes)

.800V Max800mV Max

Do the "all-inclusive" voltage drop test. Test between the battery + and the fuses.

Test connectors and connections if needed.

When all positive pigtail testing is complete, go to:

How to Test for Voltage Drop in a Battery Negative Pigtail Wire. ©

How To Test the Voltage Drop In A Battery Positive (+) Cable Pigtail Wire Attached To a BEC (Bussed Electrical Connector), or a Fuse Block

How?

How?

Back to Index

X

X

How To Test the Voltage Drop Between Battery Positive (+) Terminal and Fuses

DVOM + Clipped to Battery Positive +

DVOM (-) on topof any active fuse

DVOM (-) on top of any different active fuse

This Result143mV

This Result138mV

This all-inclusive test checks for any serious voltage drops between the battery positive terminal and the connections to fuses in the fuse box or BEC – bussedelectrical connector. Select two or more fuses that are active with engine running. You should see close similarity between the voltage drops of all fuses active. The more current the fuse tested sees, the higher the voltage drop. If your meter shows charging voltage, that fuse is connected to ground, and is not active until whatever it protects is activated. Consult the fuse box or BEC cover for fuse description.

Meter set to millivoltsEngine RunningIn ParkAt Idle300mV Maximum

Back to TestingBattery + Pigtail(Notes)©

How to Test for Voltage Drop in a Battery Negative (-) Cable Pigtail Wire.

Do the "all-inclusive" voltage drop test.

If excessive: Test of connectors and connections if needed.

With all voltage drop testing complete on the Battery Negative (-) Pigtail wire go to:

How to Test for Voltage Drop in Ground Straps that are Not Directly Attached to the Battery Negative Cable.

How?

How?

©Back to

Index

X

X

Battery negativepigtail ground wireVoltmeter (-) probe

on clean battery (-)post or side mount,NOT on cable clamp

Voltmeter (+) onclean sheet metal

NEAR pigtailconnection,NOT on bolt

or pigtail eyelet

Set Voltmeter to read millivolts or on the lowest volt

setting.

Engine OFFturn on all

accessories.Maximum allowable

voltage drop100mV.100V

100mV Maximum.100V Maximum

Follow same procedure if the negative pigtail is attached to frame metal ©

How to Test the Voltage Drop Between the Battery Negative (-) Terminaland a Battery Negative (-) Pigtail Attached to Sheet or Frame Metal

Back(Notes)

Do an "all-inclusive" voltage drop test between the bulkhead ground strap and the battery negative terminal.

If excessive: Test between the bulkhead and the block if needed.

Test between battery negative terminal and where the negative cable is attached to the frame or block if needed.

Test between the battery negative cable and terminal if needed.

Test between the cable and the cable eyelet material.

Test between sheet metal cab to bed if needed.

With all grounds checked, go to:

How to test the generator voltage feed side.

How to Test the Voltage Drop in Ground Straps that are Not Directly Attached to the Battery Negative Cable.

How?

How?

How?

How?

How?

Back to Index

How?

X

X

Voltmeter set to read millivolts or on the lowest volt setting.Engine OFF, all accessories on.

Voltmeter negative (-) probe on a clean spot on the post top or sidemount nut, NOT on cable or clamp

Voltmeter positive (+) probe on a clean spot NEAR the bulkhead ground strap attaching point, NOT on cable, eyelet, or nut.

.300V Maximum300mV Maximum

How to Test the Voltage Drop Between the Battery Negative Terminal and the Bulkhead (firewall) Ground Strap

Back©(Notes)

Do the "all-inclusive" voltage drop test.

If excessive:

Test connectors and connections if needed.

When the voltage feed side of the generator testing is complete, go to:

How To Test For Voltage Drop In The Generator Ground.

How to Test the Voltage Drop Between the Generator Output and the Battery Positive (+) Terminal

How?

How?

©Back toIndex

X

X

Voltmeter (-) toBattery (+) SideMount Nut or Top of Post, NOTon cable or clamp.

Voltmeter (+) probe to generator side of B+ wire connection, NOT on outside nut, cable connector, or stud.

200mV (.200V) Maximum

Set voltmeter to readmV DC

Run engine at1800 RPM

for 30 seconds,now, read meter.

This in an “all-inclusive” test.This test checks for voltage drop between the following conductors and connections: the connection between the B+ terminal of the generator and the wire eyelet, the connection between the wire itself and the eyelet metal, the connection or connections that may exist anywhere between the B+ terminal of the generator and the battery positive (+) terminal.

How to Test the Voltage Drop Between:the Generator Output and the Battery Positive (+) Terminal

Back©

(Notes)

How To Test the Voltage Drop of Connectors and Connections Of Battery Positive Pigtail Wires.

Voltmeter set to millivoltsMeter Positive Probe toGenerator Side of B+ StudConnection.

Voltmeter negative probe ona T-pin in correct pigtail wirethat goes to battery positive.It is one of these three on thisvehicle. Check wiring diagram.T-pin here, or closer to generator if available.

(Notes)

Engine running, all accessories on. Should be zero voltage drop. Less than 50mV would be of no concern. Back

Do the “all-inclusive” voltage drop test.If excessive:

Test between the generator housing and the block if needed.

Test between the block and the battery negative terminal if needed.

Test between the negative cable and its connector if needed.

Test between the negative cable clamp and the battery terminal if needed.

When the generator ground testing is complete, go to:

How To Test the Voltage Drop In The Generator Ground

How?

How?

How?

How?

How?

Other generator tests. © Back toIndex

X

X

Voltmeter (+) toa clean spot on

the generatorhousing

Voltmeter (-) probe to a cleanpost top or side mount bolt,

NOT on cable or clamp

Voltmeter (+)probe to a clean

spot on thegenerator case

The generator grounds through its block mounting. This in an “all-inclusive”test. If excessive, do “parts and pieces” testing to find the problem. Don’t overlook the battery negative cable-to-block connection. ©

Set Voltmeter to readmillivolts or on thelowest volt setting

Run engine at1800RPM

for 30 seconds.Keep at 1800RPM.Now, turn on all

accessoriesfor 30 seconds.Keep them on,

and read the voltmeter.

How to Test the Voltage Drop of the Generator Ground

Back(Notes)

100mV Maximum

Test for generator charging voltage.

Test for shorted diodes with a DVOM "diode test mode“.

Test for shorted diodes with a micro-amp draw test.

Test for “AC riding on DC”.

Verify a good generator.

Other Generator Tests

How?

How?

How?

How?

How?

©

X

Next

This is the end of the program.

To go back to the beginning,

push this button:

or, to end the program,

right click the mouse,

then left click on “End Show”.

Set voltmeter to read volts DC.Put voltmeter positive (+) probeon battery (+) terminal.Put voltmeter negative (-) probeon battery (-) terminal.Run the engine at 1500 RPM, and turn on every load that canbe turned on – AC compressor, blower motor, rear window defogger, head lights, etc.Let engine run for more than1 minute after all loads are on.Source voltage will be between13.5 and 14.9 on most vehicles.If above 15volts, this could be caused by a faulty generator regulator.

How to Test the Generator Charging Voltage

Back©(Notes)

How to Verify a Good Generator

The battery must be good, and fully charged.

Run the engine 1200 rpm.

No accessories on.

Set up DVOM to accept an inductive pick up to indicate current.

Hook inductive pick up around wire that goes from the B+ terminal of the generator to the battery. Engine running, no load battery voltage should be between 13.8 and 15.3 volts. Load the battery with a carbon pile load tester across the battery terminals.Check the current output of the generator with the inductive current clamp. Loaded, a good generator will charge to within 10% of its stamped rating.If the generator is a rebuild, you cannot always trust the stamped rating. Keep in mind, that the majority of the vehicles on the road today operate efficiently with 65 amps generators. Use this figure as a guide.

Back©