26SI Series Alternator – Alternator | Caterpillar Engines Troubleshooting




Illustration 1	g00624846
Front View of the 30-SI Alternator




Illustration 2	g00624845
Side View of the 30-SI Alternator




Illustration 3	g00624843
Rear View of the 30-SI Alternator




Illustration 4	g00659616
Front View of the 34-SI Alternator




Illustration 5	g00659997
Side View of the 34-SI Alternator




Illustration 6	g00660002
Rear View of the 34-SI Alternator

Table 1
Specifications for 30-SI Alternators
Part Number Remanufactured Part Number	4N-3987 OR-5204	4N-3986 OR-5203	114-2401 OR-8997	9X-7803 OR-3749	8C-6163 OR-1699
Voltage Rating	32V	24V	24V	24V	12V
Current	60A	60A	75A	100A	105A
Application	Heavy Duty	Heavy Duty	Heavy Duty	Heavy Duty	Heavy Duty
Approved for Marine Use	Yes	Yes	No	No	Yes
Weight	11.9 kg (26.2 lb)	11.9 kg (26.2 lb)	11.9 kg (26.2 lb)	11.9 kg (26.2 lb)	11.9 kg (26.2 lb)
Polarity	Negative Ground Insulated Case	Negative Ground Insulated Case	Negative Case Ground	Negative Case Ground	Negative Ground Insulated Case
Minimum Full Load Current (Cold) at 5000 rpm	60A	54A	67.5A	94A	96A
Minimum Full Load Current (Cold) at 1500 rpm	20A	19A	26A ⁽¹⁾ ⁽²⁾	9A ⁽¹⁾ ⁽³⁾	42A
Turn-on Speed	2000 rpm	2600 rpm	3000 rpm	2600 rpm	2700 rpm
Output Voltage	36.6 ±1.5 V	28 ±1 V	27.5 ±1.0 V	28 ±1 V	14 ±0.5 V
Rotation ⁽⁴⁾	CW CCW	CW CCW	CW CCW	CW CCW	CW CCW

^( 1 )	Minimum Full Load Current (Cold) at 2000 rpm
^( 2 )	The minimum speed of the alternator should be 1800 rpm at low engine idle.
^( 3 )	The minimum speed of the alternator should be 2300 rpm at low engine idle.
^( 4 )	The rotation is viewed from the pulley.

Table 2
Specifications for 34-SI Alternators
Part Number	169-4319	167-7812	165-5140	167-7816
Voltage Rating	24V	24V	24V	12V
Current	75A	75A	100A	110A
Application	Heavy Duty Pad Mount	Heavy Duty	Heavy Duty	Heavy Duty
Approved for Marine Use	Yes	Yes	Yes	Yes
Weight	11.9 kg (26.2 lb)	11.9 kg (26.2 lb)	11.9 kg (26.2 lb)	11.9 kg (26.2 lb)
Polarity	Negative Ground Insulated Case	Negative Ground Insulated Case	Negative Ground Insulated Case	Negative Ground Insulated Case
Minimum Full Load Current (Cold) at 5000 rpm	67.5A	67.5A	94A	99A
Minimum Full Load Current (Cold) at 1500 rpm	26A ⁽¹⁾ ⁽²⁾	26A ⁽¹⁾ ⁽²⁾	9A ⁽¹⁾ ⁽²⁾	42A
Turn-on Speed	3000 rpm	3000 rpm	2600 rpm	2700 rpm
Output Voltage	28 ±1 V	28 ±1 V	28 ±1 V	14 ±1 V
Rotation ⁽³⁾	CW CCW	CW CCW	CW CCW	CW CCW

^( 1 )	Minimum Full Load Current (Cold) at 2000 rpm
^( 2 )	The minimum speed of the alternator should be 1800 rpm at low engine idle.
^( 3 )	The rotation is viewed from the pulley.

Table 3
Torque Specifications for the 30-SI Alternator
Part Number Remanufactured Part Number	4N-3987 OR-5204	4N-3986 OR-5203	114-2401 OR-8997	9X-7803 OR-3749	8C-6163 OR-1699
Pulley Nut	102 ± 7 N·m (75 ± 5 lb ft)	102 ± 7 N·m (75 ± 5 lb ft)	102 ± 7 N·m (75 ± 5 lb ft)	102 ± 7 N·m (75 ± 5 lb ft)	102 ± 7 N·m (75 ± 5 lb ft)
Cover for the Rectifier	5.3 N·m (47 lb in)	5.3 N·m (47 lb in)	5.3 N·m (47 lb in)	5.3 N·m (47 lb in)	5.3 N·m (47 lb in)
Cover Plate Regulator and Mounting Plate Heat Sink	3 N·m (27 lb in)	3 N·m (27 lb in)	3 N·m (27 lb in)	3 N·m (27 lb in)	3 N·m (27 lb in)
+ Battery Terminal	7.1 ± .8 N·m (62.8 ± 7.1 lb in)	7.1 ± .8 N·m (62.8 ± 7.1 lb in)	7.1 ± .8 N·m (62.8 ± 7.1 lb in)	7.1 ± .8 N·m (62.8 ± 7.1 lb in)	7.1 ± .8 N·m (62.8 ± 7.1 lb in)
– Battery Terminal	6.2 ± .6 N·m (54.9 ± 5.3 lb in)	6.2 ± .6 N·m (54.9 ± 5.3 lb in)	6.2 ± .6 N·m (54.9 ± 5.3 lb in)	6.2 ± .6 N·m (54.9 ± 5.3 lb in)	6.2 ± .6 N·m (54.9 ± 5.3 lb in)
“R” Terminal Nut for the Regulator Stud	2 N·m (18 lb in)	2 N·m (18 lb in)	2 N·m (18 lb in)	2 N·m (18 lb in)	2 N·m (18 lb in)
Nut for the Hex Mounting Bolt Bolt for the Adjusting Lug	88 N·m (65 lb ft)	88 N·m (65 lb ft)	88 N·m (65 lb ft)	88 N·m (65 lb ft)	88 N·m (65 lb ft)
Frame Bolts	6.2 N·m (55 lb in)	6.2 N·m (55 lb in)	6.2 N·m (55 lb in)	6.2 N·m (55 lb in)	6.2 N·m (55 lb in)
Ground Screw	6 N·m (55 lb in)	6 N·m (55 lb in)	6 N·m (55 lb in)	6 N·m (55 lb in)	6 N·m (55 lb in)

Table 4
Torque Specifications for the 34-SI Alternator
Part Number	169-4319	167-7812	165-5140	167-7816
Pulley Nut	102 ± 7 N·m (75 ± 5 lb ft)	102 ± 7 N·m (75 ± 5 lb ft)	102 ± 7 N·m (75 ± 5 lb ft)	102 ± 7 N·m (75 ± 5 lb ft)
Cover for the Rectifier	5.3 N·m (47 lb in)	5.3 N·m (47 lb in)	5.3 N·m (47 lb in)	5.3 N·m (47 lb in)
Cover Plate Regulator and Mounting Plate Heat Sink	3 N·m (27 lb in)	3 N·m (27 lb in)	3 N·m (27 lb in)	3 N·m (27 lb in)
+ Battery Terminal	7.1 ± .8 N·m (62.8 ± 7.1 lb in)	7.1 ± .8 N·m (62.8 ± 7.1 lb in)	7.1 ± .8 N·m (62.8 ± 7.1 lb in)	7.1 ± .8 N·m (62.8 ± 7.1 lb in)
– Battery Terminal	6.2 ± .6 N·m (54.9 ± 5.3 lb in)	6.2 ± .6 N·m (54.9 ± 5.3 lb in)	6.2 ± .6 N·m (54.9 ± 5.3 lb in)	6.2 ± .6 N·m (54.9 ± 5.3 lb in)
“R” Terminal Nut for the Regulator Stud	2 N·m (18 lb in)	2 N·m (18 lb in)	2 N·m (18 lb in)	2 N·m (18 lb in)
Nut for the Hex Mounting Bolt Bolt for the Adjusting Lug	88 N·m (65 lb ft)	88 N·m (65 lb ft)	88 N·m (65 lb ft)	88 N·m (65 lb ft)
Frame Bolts	6.2 N·m (55 lb in)	6.2 N·m (55 lb in)	6.2 N·m (55 lb in)	6.2 N·m (55 lb in)
Ground Screw	6 N·m (55 lb in)	6 N·m (55 lb in)	6 N·m (55 lb in)	6 N·m (55 lb in)

The results for a 12 volt 30-SI and 34-SIAlternator’s rotor field winding test at 27 °C (80 °F) are in the following list:

The results for a 24 volt 30-SI and 34-SIAlternator’s rotor field winding test at 27 °C (80 °F) are in the following list:

The results for a 32 volt 30-SI Alternator’s rotor field winding test at 27 °C (80 °F) are in the following list:




Illustration 7	g00650373
30-SI Alternator Schematic (Negative Ground Model)




Illustration 8	g00624983
34-SI Alternator Schematic (Negative Ground Model)




Illustration 9	g00625062
34-SI Alternator Schematic (Insulated Model)

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