This Bulletin might be helpful
Technical Service
Bulletin
Important: The information contained in this bulletin is intended for use by trained, professional technicians who have the proper tools, equipment, and training to perform
the required maintenance described above. This information is NOT intended for ‘do-it-yourselfers’, and you should not assume that this information applies to your
equipment. If you have any questions regarding this information please visit our website at www.prestolite.com, or contact our technical service department at:
Leece-Neville Heavy Duty Systems
400 Main Street
Arcade, NY 14009
Phone: (866) 288-9853
Fax: (866) 288-9853
webmail@prestolite.com
Source: Leece-Neville Heavy Duty Systems Division -
Arcade, NY USA
Date: November 10, 2005
Subject: On Vehicle Alternator Troubleshooting
Bulletin No: TSB-1019
Models: All 12 Volt Alternators
Less than 12.4
Volts.
STOP
Charge or replace
batteries
Note Voltage:
Must be higher
than
12.4 Volts
Voltage =
Step 1: Visual Inspection. See Procedure 1.1. of TSB-1021
Step 2: Battery State of charge: (Engine OFF) always remove surface charge
from batteries. To do this either, attach a carbon pile and load the batteries at
25% of the total CCA rating for 15 seconds or switch the headlamps on; select
high beam for 2 to 3 minutes per battery, then switch off head lamps. Allow the
batteries to recover for 30 seconds, then test the batteries true state of charge
with a volt meter. When surface charge has been removed and battery voltage
is found to be below 12.40 volts, charge or replace batteries before proceeding.
Step 3: Battery voltage verification at alternator output terminals. Ensure
that battery voltage is present when measured at the alternator positive (+)
and negative (-) out put terminals. This should be inspected with the engine
off and all electrical accessories in the off position. This voltage should be the
same as battery voltage measured in the above step. If the volt meter indication
is 1 volt less than battery voltage, complete individual cable voltage drop test
on the positive and negative cables. Correct voltage drop before proceeding. Refer to Prestolite
training manual or CD. Section 3:2 Alternator cable test for instructions to perform cable test.
Step 4: Alternator voltage test. Connect the test leads of a volt meter to the alternator output
terminals. Note: Most Leece Neville alternators have isolated ground rectification. Always
connect tester / volt meter directly to the negative output terminal of alternator or your test
will be inaccurate.
• Start engine increase to high idle 1500 RPM: The volt meter should now indicate alternator
out put voltage has increased to a range from 13.8 volts to 14.2 volts. (Ensure that all electrical
accessories of the vehicle are in the off position.) “If” voltage increases but is out of range,
Inspect to see if alternator has an adjustable regulator. If so: reduce engine speed to idle.
“Adjust voltage to a setting of 14.0 volts”. If voltage is higher than 14.7 volts and cannot be
adjusted below 14.25 volts, or if voltage is lower than 13.8 volts and cannot be adjusted into
range; replace alternator.
Technical Service
Bulletin
Bulletin No.: TSB-1019
Page 2 of 2
Important: The information contained in this bulletin is intended for use by trained, professional technicians who have the proper tools, equipment, and training to perform
the required maintenance described above. This information is NOT intended for ‘do-it-yourselfers’, and you should not assume that this information applies to your
equipment. If you have any questions regarding this information please visit our website at www.prestolite.com, or contact our technical service department at:
Leece-Neville Heavy Duty Systems
400 Main Street
Arcade, NY 14009
Phone: (866) 288-9853
Fax: (866) 288-9853
webmail@prestolite.com
Note Voltage with
load applied:
Voltage =
Subtract from
above
=
If less than
.50 Volt
OK
Note Voltage
Increase:
Must be 13.8 to
14.2 volts.
Voltage =
Amperage Load Table
Use load of Alt Rating
40 Amp 65-90
80 Amp 100-140
120 Amp 160-175
140 Amp 200-360
• Inspect: If the alternator incorporates an ignition/”IGN” terminal
this terminal must have battery voltage present above 12.4 volts. If
not; inspect circuit for open and repair. Additionally if the alternator
incorporates a DUVAC / Remote Sense “S” terminal inspect to see
that this terminal also has voltage present 12.40 volts or above. If not
inspect circuit for open and repair. If all is verified and alternator voltage
has not increased or is out of range replace alternator. If within range go to
Step 5.
Step 5: Performance Test. Set engine speed to 1500 RPM.
• With either a carbon pile or with truck accessories apply a current load
equal to 75% of rated output capacity of the alternator and maintain load
for 5 to 10 seconds. Test voltage after 10 seconds with a volt meter at the
alternator output terminals.
• Note voltage.
If truck accessories are utilized for current loading this must be monitored
with an inductive current device on the positive output cable of the
alternator. (Note applying a load greater than 80% of rated output
capacity of alternator will cause the test to be inaccurate.) The voltage
should not decrease more than .50 volts if the alternator is in good
working condition. If voltage drops more than .50 volts the alternator is considered to be
defective.
