ACDelco 26 SI User Manual

26-SI ALTERNATOR

PRODUCT INFORMATION 1/98

1G/287 4/96

PAGE

1G-287

26 SI

HEAVY DUTY

BRUSHLESS ALTERNATOR

SERVICE MANUAL

PAGE 1G-287 4/96

SPECIFICATIONS:

MAXIMUM SPEED:

Continuous: 10,000 rpm Intermittent: 12,000 rpm

AMBIENT TEMPERATURE LIMITS:

-40°C to +85°C (-40°F to + 185°F)

TRANSIENT VOLTAGE LIMITS:

100V - 300 ms (12-volt) 250V - 300 ms (24-volt)

POLARITY: Negative Ground ROTATION:

Clockwise or Counterclockwise

26-SI ALTERNATOR

FEATURES

198.0 mm

302.5 mm

26-5010

WEIGHT: 27.6 lbs (12.5 kg) MOUNTING SPAN: SAE Standard J180

Built-In Voltage Regulator

Solid-State Integrated Circuit Flat Temperature-Compensated Low Parasitic Draw Low Turn-On Speed

Improved RFI Suppression Load Dump Protection

Brushless Construction

Stationary Field Coil No Brushes or Slip Rings

Relay

Terminal

Output

Terminal

“Inside-Cooled” System

Baffled Air Inlet Sealed Live Parts Prevents entry of large or foreign material

Corrosion Protection

Sealed Rectifier-End Assembly Brass Output Terminal Hardware

Applications

Line-Haul Diesel Trucks Large Commercial Diesel Engines Harsh Environments Heavy Belt Loads and Vibrations

Extra-Large

Grease Reservoir

Stationary

Field Coil

Die Cast

Aluminum

Fan

Sealed Regulator and

Rectifier Compartment

Air Inlet

Baffles

Rectifiers

Heavy-Duty

Roller Bearing

Heavy-Duty

Sealed

Ball Bearing

26-5006

26-SI ALTERNATOR

1G/287 4/96

PRODUCT INFORMATION AND SERVICE MANUAL

26-SI HEAVY DUTY BRUSHLESS ALTERNATOR

CONTENTS

Introduction ............................................................... 1

Features ..................................................................... 2

Operating Principles.................................................. 3

Troubleshooting ........................................................ 3

A. All Charging Systems .................................... 4

B. Systems with Indicator Light......................... 4

C. Systems without Indicator Light.................... 5

D. R Terminal Accessory Problems ................... 5

E. No Output ....................................................... 5

F. Rated Output Check ....................................... 6

Alternator Unit Repair............................................... 7

Disassembly and Bench Checks ......................... 7

Final Disassembly............................................... 11

Alternator Assembly ................................................. 12

DE Frame and Rotor ........................................... 13

Rectifier End Housing and Components ............ 13

Final Alternator Assembly ................................. 16

Alternator Bench Test......................................... 19

Alternator Mounting .................................................. 21

Service Parts.............................................................. 25

Alternator Specifications........................................... 26

alternator rpm are also acceptable. The ambient temperature range for proper operation is -34°C to +85°C (-30°F to +185°F).

PAGE

26-5008

Figure 1. 26-SI Alternator

INTRODUCTION

The 26-SI series alternator is a brushless, heavy-duty integral charging system with built-in diode rectifier and voltage regulator, producing DC current for battery electrical systems. The 26-SI series is designed for use on large and mid-range diesel and gasoline engines in over the-road service, as well as for off-road, agricultural, and construction equipment.

The solid state, integrated circuit voltage regulator built into the 26-SI alternator limits system voltage by switching the ground circuit for the rotor field on and off. When the ground circuit is on, field current passes from a diode trio through the stationary field coil. Nominal regulated voltages of 13.8, 14.0, and 14.2 volts are available for 12 volt systems, and 27.5 volts for 24-volt systems.

For 12-volt systems, an output rating of 85 amperes is standard. For 24-volt systems, output ratings of 50 or 75 amperes are available. Refer to Figure 2 for graphs of typical outputs over a range of alternator speeds. For output ratings of specific 26-SI models refer to the Specifications section of this manual.

140

120 100

A M P

80 E R

85 amp 12V

75 amp 24V

50 amp 24V

The 26-SI alternator may be operated in either clockwise or counterclockwise directions (external fan may require changing to reverse rotation) at continuous speeds of up to 10,000 alternator rpm. Intermittent speeds of up to 12,000

1 2 3 4 5 6 7 8 RPM x 1000

26-5009

Figure 2. Typical Output vs. Alternator RPM

PAGE 1G-287 4/96

FEATURES

The 26-SI alternator is designed for a “one-wire” charging system configuration. “One-wire” refers to the minimum number of lead wire connections necessary at the alternator for operation and requires only that the alternator output terminal be connected to the battery insulated (positive for a negative-ground system) terminal and that a ground path be provided between the alternator housing and the battery ground terminal. (See Figure 3)

OUTPUT

TERMINAL

(B+)

26-SI ALTERNATOR

GROUND

"R" or "I"

TERMINAL

GENERATOR

BATTERY

26-5011

Figure 3. Basic One-Wire System

Some applications use an “I” terminal circuit to power an indicator light and/or to lower the engine speed (RPM) at which the alternator will turn on. Typical system wiring using this type of circuit is shown in Figure 4. This is commonly referred to as a “one-wire system with I terminal” or as a “two-wire system.”

GENERATOR

BATTERY

26-5012

Figure 4. One-Wire System with I Terminal

External connections to the 26-SI alternator are made to

terminals shown in Figure 5. The standard output terminal is a “female” type with insulated connecting bolt and charge lead cable with a special connector. When installed, the electrical connection is sealed from moisture and there are no exposed parts with battery voltage. The connector bolt head is normally stamped “No Volts” to indicate the insulated type.

26-5013

Figure 5. 26-SI Electrical Terminals

Some 26-SI models use a 1/4" threaded stud type of output terminal. With this type of terminal, the exposed metal parts are not insulated and will have battery voltage when connected to the battery.

Optional connections to the 26-SI series include either an “R” (relay) or “I” (indicator light) terminal, and a ground lead connection to the alternator’s rectifier end housing.

An “R” or relay terminal is located on the side of the alternator opposite from the output terminal. This terminal may be used to operate some types of charge indicators, an ADLO system, a tachometer, or similar device by providing voltage pulses at a frequency of 8 pulses for each revolution of the alternator. The current draw of the accessories being powered through this terminal must not exceed 4 amperes. “R” terminals are normally of the unthreaded pin type.

When an “I” terminal is present it will be located on the side of the alternator opposite from the output terminal, in place of the “R” terminal. An “I” terminal is connected internally to the field circuit. An indicator light connected in series with this terminal will glow whenever there is a voltage difference between the “positive” side of the field circuit and the system voltage at other side of the indicator light. During normal alternator operation, the light will be off since the diode trio output voltage equals the system voltage. A side benefit of this circuit is that current is passed through the field winding during engine start-up, resulting in a lower alternator turn-on speed. A diode or resistor may be used instead of a light bulb if no indicator light is needed. (See Fig. 4) Up to 1 ampere of current may

26-SI ALTERNATOR

1G/287 4/96

PAGE

be passed through this circuit to aid in alternator turn-on. An “I” terminal is normally a threaded stud type with a 1024 thread.

A threaded 1/4" hole (with screw and lockwasher) in the rectifier end housing between the output and “R” or “I” terminal is provided to connect a ground lead if used; otherwise, the ground path is through the mounting hardware and brackets to the engine. On replacement units, a paper tag is present identifying the “ground screw”; remove and discard the tag. The screw and lockwasher should be installed in the housing regardless of whether a ground lead is connected, to prevent entry of dirt and water.

All electronic parts of the alternator are sealed in a compartment to keep out moisture and dirt, and the alternator is “inside cooled” by air drawn through a baffled inlet in the rectifier end cover and exiting from the drive end frame behind the fan.

OPERATING PRINCIPLES

An alternator is a voltage-creating machine. The voltage regulator limits the maximum voltage that the alternator will produce at the output terminal by controlling the

induce voltages in the stator windings. The faster the rotor turns, the higher the induced voltage will be.

The initial voltages at start-up are generated by residual magnetism in the rotor. On applications with an “I” terminal in use, this magnetism will be boosted by a small amount of current flowing through the field from the indicator light circuit. As speed and output increase, voltage available at the diode trio becomes sufficient to supply field current for normal operation. When the output voltage exceeds the battery voltage, the alternator begins to drive the system voltage. If the wiring system includes an indicator light, the presence of system voltage at the diode trio equalizes the voltage on both sides of the indicator light and the light goes out.

While the system voltage is below the voltage regulator setting, the regulator turns on the field current and allows the alternator to produce as much output as possible for the alternator speed (rpm), temperature and system voltage. When the voltage setting is reached, the regulator turns the field current off. When the field current is turned off, the magnetic field in the rotor collapses and the alternator output voltage begins to fall. The falling voltage causes the regulator to turn the field current back on and the magnetic field to rebuild. This switching action of the

REGULATOR

CAPACITOR

DIODE TRIO

ROTOR

STATOR

RECTIFIER BRIDGE

R B+

B-

26-5014

Figure 6. Alternator Schematic with R Terminal

magnetic field present in the stationary field. The output voltage, induced in the stator and rectified by the diodes, allows current to flow to satisfy the electrical loads placed on the system, up to a maximum current that is characteristic of the alternator design.

Schematics of the alternator circuitry are shown in Figure 6 (with “R” terminal) and Figure 7 (with “I” terminal). With the alternator rotor turning, a magnetic field around the stationary field coil is conducted by the rotor poles to

REGULATOR

DIODE TRIO

ROTOR

STATOR

RECTIFIER BRIDGE

CAPACITOR

GROUND

B+

B-

26-5015

Figure 7. Alternator Schematic with I Terminal

regulator continues rapidly, keeping the output and system voltage very close to the voltage setting. This will continue unless the electrical demands of the system cause the system voltage to fall below the voltage setting. Should this happen, the regulator will again allow full field current to flow so that the maximum output of the alternator at the given speed, temperature and system voltage is realized.

An internal sense lead installed between the output terminal/diode heat sink and regulator stud, is used for voltage control.

PAGE 1G-287 4/96

26-SI ALTERNATOR

TROUBLESHOOTING

Trouble in the charging system will normally be indicated by one of the following:

• Indicator light “on” with engine running.

• Indicator light “off” with key on, engine not running.

• Undercharged or overcharged battery.

• Short life of light bulbs or other electric equipment caused by abnormally high system voltage.

• System voltmeter readings outside normal range.

• Incorrect or no operation of accessories connected to alternator “R” terminal.

Diagnose system as follows: (See Fig. 8)

A. ALL CHARGING SYSTEMS -

TEST EQUIPMENT NEEDED:

• Belt Tension Gage

• Battery State-of-Charge Indicator

1. Check electrical system wiring and battery terminals for poor connections or other obvious conditions that might result in shorts, opens, grounds, or high resistance. Correct as necessary.

2. Check alternator drive belt for proper tension. Adjust to manufacturer's specifications.

3. Check battery for state-of-charge. If low, recharge according to manufacturer’s specifications and load test to establish serviceability. Further diagnostic tests require a known good, fully-charged battery for accurate results.

B. SYSTEMS WITH INDICATOR LIGHT -

TEST EQUIPMENT NEEDED:

• Jumper Lead with 5-Amp Fuse

1. If indicator light is on with engine running: Stop engine. Turn key switch to “run” position. Indicator

light should be on. If not, go to Step 3. Disconnect indicator light lead at alternator. This will

be the “I” terminal connector. If indicator light remains on, locate and correct shorted

or grounded condition in indicator light circuit between the light and the alternator.

If indicator light goes out, light is working properly. Proceed to “C.” for check of system with indicator light working properly.

2. If indicator light does not come on with the key switch in the “run” position with the engine stopped (“bulb check” mode):

Leave key in “run” position with engine stopped. Disconnect indicator light lead from alternator. This will be at the “I” terminal. Use fused (5-amp) jumper lead to ground indicator lamp circuit in harness connector to ground screw or other clean metal ground on alternator housing.

- If indicator light comes on with jumper lead in place, repair or replace alternator as described under Unit Repair.

FUSE

KEY SWITCH

TERMINAL CONNECTOR (DISCONNECTED)

BLOCK

INDICATOR LIGHT ("I") CONNECTOR

B2, B3

INDICATOR LIGHT

INDICATOR LIGHT CIRCUIT

FUSE

"R" or "I" TERMINAL

GENERATOR

OUTPUT TERMINAL

D3,E2

Figure 8. Troubleshooting a 26-SI System

VOLTMETER

BATTERY

26-5016

26-SI ALTERNATOR

1G/287 4/96

PAGE

- If indicator light does not come on with jumper lead in place, verify that alternator is properly grounded by touching jumper lead to another ground source. If lamp still does not light, locate and correct open circuit in indicator light circuit. Circuit fuse may be open or light bulb may be burned out. Correct as necessary.

3. If indicator light comes on while engine is running, but is not on with engine stopped and key switch in “run” position:

- If indicator light comes on with jumper lead in place, replace internal indicator light lead assembly or regulator as described under Unit Repair.

- If indicator light does not come on with jumper lead in place, locate and correct open circuit in indicator light circuit between battery and light. Circuit fuse may be open. (With engine running, light is being powered by alternator and grounded through other circuits connected in parallel to indicator light circuit.) Correct as necessary.

4. If indicator light is on with key switch in “off” position: Disconnect indicator light circuit at alternator.

- If voltage reading at battery terminals is different from reading showing at system voltmeter (if equipped), locate and correct cause of incorrect reading.

- If voltage is lower than reading previously recorded with engine stopped, there is no alternator output. Proceed to section on No Output.

- If voltage is higher than previous reading with engine stopped, alternator output is present. Proceed to Rated Output Check.

2. If battery is overcharged (as evidenced by excessive water use or electrolyte spewing from battery vents), or light bulbs or other electrical equipment have shortened life due to suspected high system voltage, or system voltmeter reads above normal range:

With fully charged battery, engine running at moderate speed and all electrical loads off, use voltmeter to check voltage at battery terminals.

For a 12-volt system, readings should be stable, around

13.5 - 14.5 volts and in no case go above 15 volts. For a 24-volt system, readings should be stable, around 27

- 28 volts and in no case go above 31 volts.

- One-wire system: If voltage is erratic or goes above 15 volts (31 volts on 24-volt system), check internal sense circuit and regulator as described under Unit Repair.

- If indicator light remains on, locate and correct shorted condition between the light and alternator.

- If indicator light goes out, diode is shorted in rectifier. Locate and replace diode as described under Unit Repair.

C. SYSTEMS WITH VOLTMETER, NO INDICATOR

LIGHT, OR WITH LIGHT WORKING PROPERLY -

TEST EQUIPMENT NEEDED:

• Voltmeter

1. If battery is undercharged, indicator light remains on while vehicle is running, or system voltmeter shows operating voltage is below acceptable range:

With engine stopped and all electrical loads off, use voltmeter to check system voltage across battery terminals. Record voltage.

Start engine and run at moderate speed. Check system voltage across battery terminals with engine running.

D. R TERMINAL ACCESSORY PROBLEMS

1. Disconnect lead from “R” terminal.

2. Start engine and run at moderate speed. Check system voltage across battery terminals with engine running. Record voltage.

3. Use voltmeter to check voltage between “R” terminal and alternator ground screw or other clean metal ground.

- If voltage is near half of system voltage, “R” terminal output is O.K. Note that this is a pulsating signal, so some voltmeters may give an unsteady reading.

- If no voltage is present, replace diode trio assembly as described under Unit Repair.

- If voltage is nearly the same as the alternator output voltage, disassemble alternator as described under Unit Repair and check to see if terminal is connected to diode trio lead. If so, replace diode trio assembly. If terminal is connected to regulator, it is wired as an “I" terminal and can’t be used as an “R” terminal.

PAGE 1G-287 4/96

26-SI ALTERNATOR

E. NO OUTPUT

TEST EQUIPMENT NEEDED:

• Voltmeter

• Jumper Lead (18 ga. min; no fuse) Note that 26-SI alternators must be connected to a

battery for the voltage sensing circuit to allow initial turn on (refer to section on Features). When properly connected and system checks indicate a “no output” condition, use the following steps to determine if the alternator requires repair:

! IMPORTANT

On alternators with insulated output terminal, voltage in battery cable at output terminal cannot be checked by touching voltmeter to connecting bolt. Disconnect output terminal and check voltage at inner ring in terminal connector of cable.

1. For alternators without an “I” terminal in use, positive voltage at the output terminal and residual magnetism in rotor are necessary for alternator to turn on. With engine stopped, use voltmeter to verify that battery voltage is present in cable at output terminal. If not, locate and correct cause of voltage loss.

Residual magnetism in the rotor is sometimes lost during servicing of the alternator. The rotor can normally be remagnetized without removing alternator from application.

CAUTION: Do not allow jumper lead to be accidentally grounded while connected to battery insulated terminal. If the free end of this lead is accidentally touched to the alternator housing or other grounded areas, the jumper lead may quickly get hot enough to cause a skin burn or to damage the jumper lead. Keep jumper lead carefully insulated from grounding during this procedure.

To remagnetize rotor, make sure the normal connections are made to the alternator output terminal and to the ground circuit. Disconnect the wiring harness from the “R” terminal. Momentarily connect a jumper lead from battery positive to the alternator “R” (or unused “I”) terminal. (See Fig. 48) This will cause field current to momentarily flow through the field windings in the proper direction and restore magnetism. Reconnect wiring harness to “R” terminal, then recheck alternator for output.

battery

voltage present at this terminal. With “I” terminal connected and indicator lamp on, voltage will be less than battery voltage. If necessary to disconnect wiring at “I” terminal to make this check, check for battery voltage in harness wire. If voltage is present, proceed to Step 3. If no voltage is present, check “I” terminal circuit for cause of voltage loss (bulb may be burned out). Correct as necessary.

3. If no conditions have been found that might prevent the alternator from turning on (Step 1 or 2), remove alternator from engine in accordance with engine manufacturer’s instructions and proceed to Unit Repair.

F. RATED OUTPUT CHECK

TEST EQUIPMENT NEEDED:

• Voltmeter

• Ammeter (current capability at least 15 amperes

higher than alternator rating)

• Variable Carbon Pile Load Test

CAUTION: Failure to disconnect grounded battery cable at battery before removing or attaching battery cable at alternator output terminal may result in an injury. If a tool is shorted to the battery cable connector at the output terminal, the tool can quickly heat enough to cause a skin burn or the tool or cable may be damaged.

1. Refer to Fig. 9 for test equipment hookups as described in following steps. If inductive pickup (“clamp on”) type ammeter is used, place current clamp on alternator output lead and skip to Step 4. If series ammeter is used, disconnect grounded battery cable at battery first.

2. Install ammeter in series with alternator output terminal.

3. Reconnect grounded battery cable at battery.

4. NOTICE: When a 12-volt carbon pile load test is used to diagnose a 24-volt system attach load test only to 12volt potential in battery pack. Attaching a 12-volt load test to a 24-volt potential will damage the load test.

With load turned off, attach carbon pile load test across battery.

5. Attach voltmeter lead to grounded battery terminal, observing proper polarity for system. Leave other voltmeter lead open for checks at various points.

2. For systems with an “I” terminal in use, the indicator light current at this terminal will establish normal magnetism at each engine start-up. Such systems may depend on this current to help ensure a low turn-on speed of the alternator. With engine stopped and key switch in “run” position, use voltmeter to check for

6. Check and record voltage at insulated battery terminal. For multi-battery systems, check voltage of battery set connected as if in battery charging mode.

7. With all system electrical loads off, start engine and run at moderate speed (rpm).

26-SI ALTERNATOR

1G/287 4/96

PAGE

CLAMP-ON AMMETER

ALTERNATOR

Figure 9. Rated Output Check

8. Recheck voltage at insulated battery terminal. Voltage should be higher than previous reading, but below 15 volts on 12-volt system (31 volts on 24 volt system).

- If reading is lower than previous reading (Step 6), refer to section on No Output.

CARBON PILE

F6,F8

BATTERY

VOLTMETER

Maximum ampere output should be within 15 amps of output rating stamped on alternator identification plate, or as listed in Specifications section of this manual. Voltage drop should be 0.25 volts or less for each voltage drop test on 12-volt system (0.5 volts or less on 24-volt system).

26-5017

- If reading is higher than 15 volts on 12-volt system (31 volts on 24-volt system), refer to section on High Voltage Output.

9. Turn carbon pile load on and adjust to obtain maximum alternator output on ammeter. Record maximum output.

With alternator still running at maximum output, check and record voltage drop in ground circuit between alternator housing and grounded battery terminal. Then check voltage drop from output terminal to battery positive. Turn carbon pile load off.

- If ground circuit voltage drop is over 0.25 volts on 12 volt system (0.5 volts on 24-volt system), clean and tighten all ground circuit connections. If this does not correct excessive voltage drop, check ground circuit cables for improper sizing or high resistance conditions. Correct as necessary.

- If within 15 amps of rating, alternator is good. Look elsewhere for cause of problem.

- If more than 15 amps below rating, repair or replace alternator.

PAGE 1G-287 4/96

26-SI ALTERNATOR

ALTERNATOR UNIT REPAIR

CAUTION: Disconnect grounded cable at battery before removing or attaching battery cable at alternator output terminal. Otherwise, a tool shorted to the battery cable at the output terminal can quickly heat enough to cause a skin burn or damage the tool or cable.

NOTICE: Always reinstall fasteners at original

location. If necessary to replace fasteners, use only correct part number or equivalent.

• If correct part number is not available, use only equal size and strength. For alternator internal fasteners, refer to Delco Remy America Standard Hardware Fasteners section in Service Parts Catalog.

• Fasteners that are NOT to be reused will be noted in procedure.

• Fasteners requiring thread locking compound will be noted in procedure.

• Use specified torque values when shown.

CAUTION: Using or replacing fasteners in any other manner could result in part or system damage.

1. HOUSING ASSEMBLY

19. COVER

20. PLATE

32. SCREW (3)

33. SCREW (4)

34. SCREW (4)

47. GASKET

Figure 10. Removing End Plate and Cover

26-5018

If diagnosis determines that alternator repair is needed, remove alternator from engine according to manufacturer’s instructions.

DISASSEMBLY AND BENCH CHECKS

TEST EQUIPMENT NEEDED:

• Multimeter

• Regulator Tester

ALTERNATOR

1. Remove rectifier end plate (20), rectifier end cover (19), and gasket (47). (See Fig. 10)

2. Inspect electronics compartment (See Fig. 11) for contamination, for shorted or grounded wires, and for loose connections. If contamination is present, clean and dry compartment before proceeding. Check gasket for source of entry and replace as necessary.

If indicator light was not operating properly, check internal indicator light lead assembly for correct installation and continuity. Correct as necessary.

26-5019

Figure 11. Electronics Compartment

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