IK0800403 ­ Alternator Troubleshooting and Diagnostics

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7

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ELECTRICAL SYSTEM

Created:

11/1/2012

Current Language: English

Last Modified: 4/17/2014

Other Languages: NONE

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Ken Fogelstrom

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Title : Alternator Troubleshooting and Diagnostics
Applies To : All

CHANGE LOG
Dealers: Please refer to the change log text box below for recent changes to this article:
4/17/2014 - Alternator Diagnostic Worksheet was reformatted and made into a fillable PDF Form. the Form can be printed out and filled in or filled in
on your computer.

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DESCRIPTION
This document details the procedure that must be followed to assure proper Alternator troubleshooting and diagnostics.
The procedure requires the use of the MidTronics EXP tester, and the Alternator Diagnostic Worksheet.
Benefits of using this procedure are:
• Increased customer confidence that the vehicle is fixed right the first time.
• Increased productivity, through accuracy of diagnosis.
• Reduced in bay shop time, vehicle down time, and shop come backs.
• Correct diagnosis to protect against No Problem Found charge-backs after part is reviewed and tested.
• Built­in repair documentation to provide with a Warranty Claim.
WARRANTY AND CLAIM INFORMATION
IMPORTANT: If the vehicle is under warranty, please refer to WPL 14-001G for requirements that may affect a claim, before proceeding with the
repair.
When troubleshooting a suspected alternator failure, technicians must utilize the Midtronics EXP Tester, and Alternator Diagnostic Worksheet.
Critical diagnostic testing values are to be recorded on the worksheet (over the counter parts warranty when no vehicle is present to perform
diagnostics does not require the worksheet).
All alternators replaced under warranty (codes 01,03,39, and 55) may be requested back for evaluation. Any that are found to be non-defective or
unnecessarily replaced, may be charged back.
DIAGNOSTIC PROCEDURE

Step 1: Inspect tensioner, belt, and pulley
CAUTION :
Verify the Engine is turned OFF.

A. Inspect belt for cracks, missing or torn ribs, edge wear, excessive rib wear, or contamination. A worn or damaged belt should be
replaced.
B. Check belt auto-tensioner:
◦
◦
◦
◦

The Auto Tensioner Pulley should turn freely without binding
Tensioner arm should move smoothly through its entire range of motion
Should feel significant spring tension through range of motion
When installed with proper belt length the tensioner should be in mid­travel (approximately 50%)

C. Ensure proper pully nut torque, per vehicle/alternator specification.

Step 2: Inspect cables and terminals

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IK0800403 ­ Alternator Troubleshooting and Diagnostics

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A. Inspect cables and connections for loose crimps, corrosion, and damage. Repair or replace as necessary.
B. If the alternator incorporates an ignition (IGN) terminal this terminal must have battery voltage present above 12.4 volts.
i) If not, inspect circuit for open and repair.
C. If the alternator has a battery Voltage Sensing feature, verify that the sense wire is securely connected to the "S" (sense) terminal.
Note that the voltage sense wire should NOT be connected to the "L" (lamp) terminal.
i) If the sense wire was connected incorrectly, indicate this in the claim notes.

Step 3: Battery State of Charge
Perform Battery Test portion of the Midtronics System Test
A.
B.
C.
D.
E.
F.

Do the "Test Preparation" as described inSection 4 of the Midtronics EXP Instruction manual.
Select "System Test" and follow procedure for testing battery pack, as described in Section 5 of the Midtronics EXP Instruction Manual.
If testing an 8-battery system, repeat step 2(b) for the second 4-pack.
If prompted "Good pack", proceed to Step 4, below.
If prompted "Check battery pack", continue by selecting 'Break pack down', and test each battery individually as described in the manual.
If prompted to "Charge & re­test", batteries MUST be charged before proceeding with the alternator diagnostics.

Step 4: Starter & Alternator Performance Test
Continue with Midtronics System Test, Section 5, for Starter and Alternator:
A. Connect positive (+) and negative (­) test leads to batteries.
B. Following Midtronics prompts, conduct "Starter system test" and "Charging system test".
C. When prompted, choose 'Amp Clamp Available' option, if available.
D. If an alternator problem is indicated, proceed to Step 5.
i) If not, alternator is good. Do not replace. Enter "Charging System Decision" result into Alternator Diagnostics Worksheet.
END OF DIAGNOSTIC
Step 5: Circuit Test - If needed
I. If Midtronics Cable Drop Test Leads (DMM Test Leads) ARE available:
A. Connect the Midtronics DMM test leads.
B. Perform the Cable Drop Test as described in the Section 7 of the Midtronics manual.
C. Record indicated voltage drops from Midtronics tool, into the Alternator Diagnostics Worksheet.
D. If prompted by the tester, "clean and re-test", or "replace" wiring.
E. Refer to "Charging System Decision" and "Diode Decision" in Midtronics manual. Follow instructions for further inspections and re-tests.
F. If problem remains after all diagnostic steps have been exhausted, proceed to Step 6.
i) If not, alternator is good. Do not replace. Enter "Charging System Decision" result into Alternator Diagnostics Worksheet.
END OF DIAGNOSTIC
II. If Midtronics Cable Drop Test Leads (DMM Test Leads) are NOT available:
Perform the following manual voltage drop tests:

A. Positive Cable Test
1. Connect ammeter to positive alternator cable.
2. Make sure ammeter is at least 6 inches (15 cm) away from alternator, to eliminate possibility of faulty readings.
3. Connect voltmeter’s negative lead to positive terminal of alternator.
4. Connect voltmeter's positive lead to positive terminal on battery.
5. Start engine and set engine 1500 RPMs.

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IK0800403 ­ Alternator Troubleshooting and Diagnostics

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6. Turn on vehicle loads until 75% of alternator’s rated output is achieved on ammeter display.
7. If necessary, use a carbon pile tester to apply load on alternator.
8. Record measured voltage to checklist.
9. Turn off engine.

NOTE:
If reading was greater than 0.25 volts in a 12 volt circuit (or 0.50 volts in a 24 volt circuit), check all wire connections and cable
connections. Correct voltage drop before proceeding.

B. Negative Cable Test
1. Connect ammeter to positive alternator cable.
2. Verify the ammeter is at least 6 inches (15 cm) away from alternator, to eliminate possibility of faulty readings.
3. Connect voltmeter’s negative lead to negative terminal of battery.
4. Connect voltmeter's positive lead to negative output terminal on alternator.
5. Start engine and set engine 1500 RPMs.
6. Turn on vehicle loads until 75% of alternator’s rated output is achieved on ammeter display.
7. If necessary, use a carbon pile tester to apply load on alternator.
8. Record measured voltage to checklist.
9. Turn off engine.

NOTE:
If reading was greater than 0.25 volts in a 12 volt circuit (or 0.50 volts in a 24 volt circuit), check all wire connections and cable
connections. Correct voltage drop before proceeding.

C. Record measured voltage drops into the Alternator Diagnostics Worksheet.
D. Clean and tighten connections, or replace wiring as needed.
E. Refer to the table, "Charging System Decision" in the Midtronics instruction manual. Follow instructions for further inspections and re-tests.
F. If problem remains after all diagnostic steps have been exhausted, proceed to Step 6.
i) If not, alternator is good. Do not replace. Enter "Charging System Decision" result into Alternator Diagnostics Worksheet.
END OF DIAGNOSTIC

Step 6: REPLACE ALTERNATOR
A. Enter "Charging System Decision" result into Alternator Diagnostics Worksheet.
B. Perform the following inspections on the old alternator, and correct for any related problems before installing new alternator.
NOTE:
Some problems may impact warranty on this and future claims.

Action

Corrections and Warranty Determination
Part label must be intact. If label is missing or destroyed, a justifiable reason must be
presented and accepted by a representative before a claim process is initiated. A
missing or intentionally destroyed label may void the warranty.

1. Record alternator date code
If date code is newer than vehicle manufacture or in-service date, this is a
replacement part. The date code must coincide with the date of invoice when the
part was purchased, or be validated by an “install date”.

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IK0800403 ­ Alternator Troubleshooting and Diagnostics

2. Inspect for excessive dirt, grease, or oil

3. Inspect for rust and corrosion.

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Excessive dirt, grease, or oil soaked/saturated condition: Oil and grease on surface
and/or interior of alternator will prevent unit from cooling properly, causing premature
failure. This may also create a low voltage condition on the vehicle.
Check and correct any sources of excessive oil, grease, and dirt. Check for missing
shields, leaking hoses, or fraying belts.
Alternators can become rusted or corroded such that they cannot function, or
function
intermittently. Examples are positive side rectifiers shorted to case by a “corrosive
bridge”, the rotor rusted and seized to the stator, or electrical connections open due
to corrosion.

4. Inspect for damaged shaft, mounting bosses,
housing

Bent, broken, cracked or elongated mounting holes, impact marks or cracked
housings render all products unacceptable for warranty.

5. Inspect for signs of arcing or shorts to housing or
connection points.

Signs of arcing or direct shorts to housing or connection points, including hardware
dropped or loose inside of alternator housing, improperly connected or modified
electrical connectors, or cut/severed wires will void warranty.

6. Inspect mounting brackets

Make sure charging system components are securely mounted to their applicable
brackets. Brackets, in turn, must be bolted securely to the engine. Poorly mounted
charging system components lead to vibration damage and diminished drive belt
performance.

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