Heavy Duty Alternator
Charging System Troubleshooting
Alternator Charging System Troubleshooting
Squealing noises under the
hood?
Headlight bulbs blow out
repeatedly or dim?
Is the dash voltmeter gauge
out of range - either too high
or too low?
These are common indicators that
something may be wrong with the
charging system. If any of these
symptoms are evident, then follow these
five steps to pinpoint the issue.
Helpful Hint:
If you find something wrong at any
step, it’s wise to complete the remaining
steps anyway to ensure you’ve given the
charging system a thorough review.
Visit http://tinyurl.com/delcoremyvideos
to watch our Tech Tip videos
Technical Assistance 800-372-0222
1
2
3
4
5
Perform
Visual Inspection
Inspect Battery
Battery Voltage Test
Battery Load Test
Measure
Voltage at Battery
Test
Alternator Output
Troubleshoot per
Service Manual
Troubleshooting
Complete
1
Perform Visual Inspection
Perform a visual inspection under the hood
Look at the belt tension and condition. Next, check electrical connections and
cables for corrosion and proper tightness. Finally, make sure the alternator is
mounted properly.
Belt
Tension and
Condition
OK?
No
Perform Repairs
Yes
Electrical
Connections
OK?
No
Perform Repairs
Yes
Alternator
Mounted
OK?
No
Perform Repairs
Yes
Visual Inspections
Complete
Visit http://tinyurl.com/delcoremyvideos to watch the Alternator Charging System Tech Tip video
2.A
Inspect Batteries
Visually inspect and test the batteries
Inspect the batteries for any signs of physical damage, cracks in the casing, loose
terminals or leaking fluid. Clean, repair connection and replace any damaged
batteries found. Ensure that all batteries used in the same circuit are of the same
manufacturer, CCA rating type and age. Then test the batteries using a standard
battery test. Remember that realistic testing, as well as successful operation, requires
a fully charged battery, capable of supplying the starting system’s current needs.
Corrosion
or Loose
Connections?
Yes
Perform Repairs
No
Battery
Damaged?
No
Perform Battery
Voltage Test
Visual Inspection
Complete
Technical Assistance 800-372-0222
Yes
Replace Battery
2.B
Battery Voltage Test
Test the batteries using a standard battery test.
Remember that realistic testing, as well as successful
operation, requires a fully charged battery, capable
of supplying the starting system’s current needs.
12.4
DC AMP
DC VOLTS
Connect Voltmeter
to Battery
With Engine Off,
Remove Surface Charge
and Wait Two Minutes
Measure
Voltage
Visit http://tinyurl.com/delcoremyvideos to watch
the Alternator Charging System Tech Tip video
< 12.4 Volts
Recharge Battery
≥ 12.4 Volts
Perform Battery
Load Test
Battery Voltage
Test Complete
Visit http://tinyurl.com/delcoremyvideos to watch the Alternator Charging System Tech Tip video
2.C
Battery Load Test
Connect Carbon Pile
and Voltmeter
to Battery
12.5
Adjust Carbon Pile to
One-half the Cold Cranking
Amp Rating for 15 Seconds
Visit http://tinyurl.com/delcoremyvideos to watch
the Alternator Charging System Tech Tip video
Record
Lowest
Voltage
< Minimum
Loaded Voltage
≥ Minimum Loaded Voltage
Battery Passes
Battery Load
Test Complete
Technical Assistance 800-372-0222
Replace Battery
3.A
Measure Voltage at Battery
Fig 1. With the engine running, use a voltmeter
to measure voltage at the battery. If voltage is
greater than or equal to 13.8 volts, you can
move on to Step 4.
12.4
DC AMP
DC VOLTS
Fig 1
Visit http://tinyurl.com/delcoremyvideos to watch
the Alternator Charging System Tech Tip video
Fig 2. However, if it is less than 13.8 volts,
then you should measure voltage at Alternator
B+ and the alternator case. (Note: If the model
is insulated, you have to use a ground stud to
get a reading.)
13.0
DC AMP
DC VOLTS
At that point, if the voltage falls between
12.6 and 13.7 volts, you need to replace
your alternator. If it’s greater than or equal to
13.8 volts, a voltage drop test needs to be
performed.
Learn how to perform a voltage drop
test by visiting our YouTube page and
watching our Tech Tip - Voltage Drop
Test video.
Link: tinyurl.com/delcoremyvideos.
Fig 2
Visit http://tinyurl.com/delcoremyvideos to watch
the Alternator Charging System Tech Tip video
Visit http://tinyurl.com/delcoremyvideos to watch the Alternator Charging System Tech Tip video
3.B
Measure Voltage at Battery
Connect Voltmeter
to Battery
Turn Engine On
Measure
Battery
Voltage
< 13.8 Volts
Connect Voltmeter to
Alternator B+ and
Ground Post
≥ 13.8 Volts
Measure
Voltage
≥ 13.8 Volts
Perform Voltage
Drop Test
Voltage at Battery
Measured
Technical Assistance 800-372-0222
12.6 to 13.7 Volts
Replace
Alternator
4
Test Alternator Output
You can use either an automated tester or a manual process to determine the output
of the alternator. If the alternator doesn’t pass this test, then it needs to be replaced.
Connect Carbon Pile,
Ammeter and
Amp Clamp
Engine Running at
Governor Speed and
Electrical Loads Off
Visit http://tinyurl.com/delcoremyvideos to watch
the Alternator Charging System Tech Tip video
Load Carbon Pile
until Ammeter
Reads Highest Value
Record
Output
< 90% of
Rated Capacity
Replace Alternator
≥ 90% of Rated Capacity
Alternator Output
Test Complete
Visit http://tinyurl.com/delcoremyvideos to watch the Alternator Charging System Tech Tip video
5
Troubleshoot Using the Service Manual
If you’ve passed through the first four
steps, then the alternator is working as
designed and your problem is likely
caused by something external to the
alternator.
1
2
3
4
5
Perform
Visual Inspection
Inspect Battery
Battery Voltage Test
Battery Load Test
Measure
Voltage at Battery
Test
Alternator Output
Troubleshoot per
Service Manual
Troubleshooting
Complete
Remy International, Inc.
600 Corporation Drive
Pendleton, IN 46064 USA
For Technical Assistance call 1-800-372-0222
Technical Assistance 800-372-0222
delcoremy.com
Delco Remy is a registered trademark of General Motors Corporation,
icensed to Remy Inc., Pendleton, IN 46064 ©2013 Remy International, Inc.