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R

C520 Alternator

Troubleshooting Guide 

C.E. Niehoff & Co.

Page 1

TG48B

CONTENTS
Section 1:Wiring .................................................................2  

Section 2: CAN/J1939 Diagnostics ...................................3

Section 3: Basic Troubleshooting .....................................4

Section 4: Advanced Troubleshooting ..........................5-6

Battery Charging Conditions

The following conditions may be observed during cold-

start voltage tests until temperatures of electrical system 

components stabilize. The time it takes to reach optimum 

voltage and amps will vary with engine speed, load, and 

ambient temperature.

Maintenance/Low Maintenance Lead-Acid Battery:

Traditional lead acid batteries require lowest charge volt-

age of all vehicle battery chemistries. Battery cells must 

be maintained by periodically topping off with distilled 

water as required.

Maintenance-free Lead-Acid Battery:

Maintenance-free batteries are similar to Maintenance/

Low Maintenance batteries, but may require slightly higher 

charge voltage.

Deep-cycle/Marine Maintenance-free Battery:

Charge acceptance of these batteries may display charac-

teristics similar to maintenance-free batteries and may 

charge faster due to generally lower capacity relative to 

size. 

AGM (Absorbed Glass Mat) Maintenance-free Battery:

These dry-cell batteries respond better than standard 

maintenance-free batteries. If battery state of charge 

(SOC) drops to 75% or less, batteries should be 

recharged to 95% or higher separately from engine charg-

ing system to avoid damaging charging system 

components and to provide best overall performance. 

Charge acceptance of these batteries may display charac-

teristics similar to maintenance batteries, but may require 

higher charge voltage and will draw significant current (<100 

amps) when under 50% SOC.

Lithium Battery:

Lithium batteries have unique charging characteristics that 

differ from lead acid. These batteries require charging 

systems configured specifically for lithium battery chemis

-

tries. Contact CEN for more information on lithium battery 

charging systems and components.

Voltage testing: 

•  Set meter to proper scale and type (AC or DC).
•  Be sure to zero the meter scale or identify the meter 

burden by touching meter leads together. Meter burden 

must be subtracted from final reading obtained.

•  Be sure the meter leads touch source area only.  

Prevent short circuit damage to test leads or source by 

not allowing meter leads to touch other pins or exposed 

wires in test area.

•  Be sure to use CEN tools designed especially for trou-

bleshooting CEN alternators when available.

Resistance (ohm) testing: 

•  Set meter to proper scale.
•  Be sure to zero the meter scale or identify the meter 

burden by touching meter leads together. Meter burden 

must be subtracted from final reading obtained.

•  Be sure meter leads touch source area only. Allowing 

fingers or body parts to touch meter leads or source 

during reading may alter reading.

• 

Be sure reading is taken when source is at 70ºF. Read

-

ings taken at higher temperatures will increase the 

reading. Conversely, readings taken at lower tempera-

tures will decrease the reading.

•  Be sure to test directly at the source. Testing through 

extended harnesses or cable extensions may increase 

the reading.

•  "OL" as referenced in this document refers to open cir-

cuit: "infinite" resistance, typically in very high kilo- or 

megaohm range depending on meter and settings.

Diode testing:

• 

Diodes allow current to flow in one direction only. Typi

-

cal voltage drop in forward bias can range from 0.1-

0.85V. Meter should read OL in reverse bias. Check 

meter user manual for meter-specific testing guidelines.

Voltage drop testing: 

•  Measure voltage between B+ on alternator or power 

source and B- (ground) on alternator or source. Record 

reading. Move to batteries or other power source and 

measure again between B+ and B- terminals on battery 

or other power source. The difference between the two 

readings represents voltage lost within circuit due to, 

but not limited to, inadequate cable gauge or faulty con-

nections. 

• 

Voltage drop measurements must be taken with all elec

-

trical loads or source operating.

Dynamic/Live testing (Connecting power and ground to 

component to test operation/function out of circuit):

•  Connect jumper leads directly and securely to power 

source contacts of component being tested. 

•  Make any connection to power and ground at power 

supply or battery source terminals. Do not make con-

nection at component source terminals, as that may 

create an arc and damage component source terminals.

Testing Guidelines

Professional service technicians rely on the following 

guidelines when testing electrical components. 

Содержание C520

Страница 1: ...ing obtained Be sure the meter leads touch source area only Prevent short circuit damage to test leads or source by not allowing meter leads to touch other pins or exposed wires in test area Be sure t...

Страница 2: ...es field current preventing an abrupt mechani cal load on accessory drive system The soft start may take up to 20 seconds A2 215 regulator used with some of these units is flat temperature compensated...

Страница 3: ...4 J1939 Connector Pins Regulator Readout Expected Reading TABLE 2 A2 326 Regulator J1939 Readout Diagnostics seeTable 3 Alternator Output Voltage 28 V System Alternator Speed Regulator Temperature Alt...

Страница 4: ...s to normalize operating temperature 6 Observe charge volts and amps Charge voltage should increase and charge amps should decrease If charge voltage does not in crease within ten minutes continue to...

Страница 5: ...for system voltage at IGN terminal on regulator If OK replace regulator If not OK check vehicle wiring and ignition circuit Energize signal present alternator not rotat ing or alternator speed too low...

Страница 6: ...ective T T Alternator is defective T T With key off engine off Does battery voltage exist at alternator B terminal Yes No Repair vehicle harness circuit to B terminal on alterna tor T T Momentarily 1...

Страница 7: ...f these test procedures or if you need to locate a Factory Authorized Service Distributor please contact us at C E Niehoff Co 2021 Lee Street Evanston IL 60202 USA TEL 800 643 4633 USA and Canada TEL...

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