Section 9.2
Battery Charging Alternator

The battery charging alternator provides a source of electrical current for maintaining the storage battery in a charged condition and supplies sufficient current to carry any other electrical load requirements up to the rated capacity of the alternator.‪

The battery charging circuit consists of an alternator, with an integral voltage regulator, a battery(s) and the connecting wiring. See Figure "Typical Alternator and Related Parts — Trucks " for parts of the battery charging alternator system.‪

Figure 1. Typical Alternator and Related Parts — Trucks

Detroit Diesel has released a new alternator mounting bracket for the engine models built model year 2002 and later, mounting bolt torque specifications remain standard. See Figure "Alternator Mounting Bracket for Series 60 Model Year 2002 and Later" and Figure "Tensioner and Related Parts Series 60 Model Year 2002 and Later " .‪

Figure 2. Alternator Mounting Bracket for Series 60 Model Year 2002 and Later

Figure 3. Tensioner and Related Parts Series 60 Model Year 2002 and Later

The hinge mounted 25 - SI and 33 – SI alternators and the bracket mounted 50 DN alternator are alternating current (AC), self-rectifying units. See Figure "Alternator Mounting" .‪

Figure 4. Alternator Mounting

On engines equipped with the SI series Delco-Remy alternators, the voltage regulator is typically electronic and is located inside the alternator. Refer to the appropriate manufacturer's service instructions for complete regulator and alternator servicing information.‪

The alternator is front mounted and belt driven using the accessory drive pulley. The accessory drive pulley is gear driven by the bull gear. Refer to "1.35 Accessory Drive" for accessory drive information.‪

In 1995, the former 50 DN alternator drive system replaced the early 50 DN alternator drive system previously used on coach engines. The changes to the drive system took effect with the engine serial numbers listed in Table "Effectivity of Improved 50 DN Alternator Drive System Changes" .‪

The former 50 DN alternator drive system included a new tensioner assembly, support plate, tensioner adjusting bolt, alternator assembly and accessory drive assembly. The top pulley of the tensioner assembly is the same size as the bottom pulley (127 mm), and all pulleys in the system had front and back flanges to insure proper belt positioning during installation and improved belt tracking during engine operation.‪

The early and former tensioner assembly, support plate, and tensioner adjusting bolt are not separately interchangeable on a part-for-part basis and should not be used on an engine.‪

To simplify installation of the DN alternator drive belt and ensure proper running tension throughout drive belt life, an auto belt tensioner assembly replaced the former tensioner/support plate assembly on December 15, 1997, effective with engine serial number 6R392714. See Figure "Auto Belt Tensioner Assembly with 50 DN Alternator" . Use of the auto tensioner eliminates the need for periodic belt tension inspection. Only the auto belt tensioner assembly is used on engines with 50 DN alternators.‪

Figure 5. Auto Belt Tensioner Assembly with 50 DN Alternator

Effective June 2000, the No. 4 size vent hose on the 50DN alternator was replaced by a No. 6 braided hose to improve venting of the alternator and extend alternator life. In addition, the vent line connection point on the engine was moved from a tapped hole in the gear case to a tapped hole in the auto belt tensioner mounting plate. ‪

Section 9.2.1
Repair of Alternator

Refer to the OEM guidelines for alternator repair procedures.‪

Section 9.2.2
Removal of Alternator

Precleaning is not necessary.‪

Remove the alternator as follows:‪

ELECTRICAL SHOCK ‪
To avoid injury from electrical shock, follow OEM furnished operating instructions prior to usage.‪

1. Disconnect the cables at the batteries. Tag each lead to ensure correct connection when the alternator is reinstalled.
2. If the alternator has more than the output cable lead, disconnect all other leads from the alternator, and tag each one to ensure correct installation.
3. Remove the alternator output cable.
4. Remove the drive belts. See Figure "Typical Alternator and Related Parts — Trucks " .
5. If an auto belt tensioner assembly is installed, use a breaker bar with a 3/4 inch drive to rotate the tensioner pulley upward to relieve belt tension.

   PERSONAL INJURY ‪
   To avoid injury to hands and fingers from the spring-loaded auto belt tensioner violently snapping back, do not cut the belt to remove it.‪

6. If an auto belt tensioner assembly is not installed, loosen the alternator mounting bolts and adjusting rod nut to allow slack in the drive belts.
7. If an oil-cooled alternator is installed, disconnect the oil supply, return, and vent lines. Plug the ends of the oil lines and the oil inlet and outlet on the alternator to prevent the entrance of dirt.See Figure "Current Coach Alternator and Related Parts " for former or see Figure "Former Coach Alternator and Related Parts" for current.
8. If required remove bolt or bolts from auto belt tensioner and remove tensioner.
   

   1. Pulley Nut‪	10. Alternator Bracket Support‪
   2. Alternator Mounting Bracket‪	11. Bolt, Support to Block (2)‪
   3. Washer (4)‪	12. Bolt, Bracket Support (2)‪
   4. Bolt, Bracket to Alternator (4)‪	13. Oil Drain Tube Connector‪
   5. Bolt, Bracket to Front Cover (3)‪	14. Oil Drain Tube‪
   6. Nut (3)‪	15. Alternator Pulley‪
   7. Alternator Vent Hose‪	16. Washer‪
   8. Alternator‪	17. Woodruff Key (2)‪
   9. Oil Supply Tube‪	‪

   Figure 6. Former Coach Alternator and Related Parts

   

   1. Pulley Nut‪	11. Alternator‪
   2. Alternator Mounting Bracket‪	12. Oil Supply Tube‪
   3. Washer (4)‪	12. Alternator Brace Bracket‪
   4. Bolt, Bracket to Alternator (4)‪	14. Bolt, Support to Block (2) ‪
   5. Bolt, Bracket to Front Cover (3)‪	15. Bolt, Bracket Support (2)‪
   6. Nut (3)‪	16. Oil Drain Tube Connector‪
   7. Auto Tensioner‪	17. Oil Drain Tube‪
   8. Idler Assembly‪	18. Alternator Pulley‪
   9. Auto Tensioner Mount‪	19. Washer‪
   10. Alternator Vent Hose‪	20. Woodruff Key (2)‪

   Figure 7. Current Coach Alternator and Related Parts

9. While supporting the alternator, remove the adjusting rod bolt and hardened washer. See Figure "Typical Alternator and Related Parts — Trucks " .
10. Remove the nut and washer at the rear alternator mounting flange.
11. While supporting the alternator, remove the alternator-to-bracket bolt to prevent it from falling. See Figure "Typical Alternator and Related Parts — Trucks " .
12. Remove the two woodruff keys, if equipped.
13. Remove and retain the alternator pulley locknut, alternator pulley, and fan from the unit. See Figure "Typical Alternator and Related Parts — Trucks " .

Section 9.2.2.1
Inspection of Alternator

Refer to OEM guidelines for alternator inspection procedures.‪

Section 9.2.3
Installation of Alternator

Install alternator as follows:‪

1. Install alternator mounting bracket to the gearcase, if it was removed. Torque the mounting bolts to 58–73 N·m (43–54 lb·ft). See Figure "Typical Alternator and Related Parts — Trucks " , for engines built model year 2002 and later see Figure "Alternator Mounting Bracket for Series 60 Model Year 2002 and Later" and Figure "Tensioner and Related Parts Series 60 Model Year 2002 and Later " .
2. If a 50 DN alternator is used, install the pulley and locknut to the alternator (if removed). See Figure "Former Coach Alternator and Related Parts" for former or see Figure "Current Coach Alternator and Related Parts " for current. If an air cooled alternator is used, install the fan, drive pulley and locknut to the alternator (if removed). Torque the pulley retaining nut to 305 N·m (225 lb·ft).
3. If the pulley was not removed, check the retaining nut for proper torque. Torque the retaining nut to 305 N·m (225 lb·ft), as necessary.
4. If the pulley was removed during disassembly, install two woodruff keys in the mounting bracket.
5. Position the alternator on the mounting bracket, and align the holes in the alternator mounting flanges with the tube in the bracket support.

   Note: There are two holes in the front alternator end frame mounting flanges. One is threaded and one is not threaded. The threaded hole is positioned up and is used to secure the alternator to the adjusting rod.

6. Install the alternator-to-bracket bolt and locknut. Insert the adjusting rod bolt, with washer installed, through the adjusting rod bracket and into the threaded hole in the alternator end frame. Finger-tighten both bolts. See Figure "Typical Alternator and Related Parts — Trucks " .
7. If the alternator is oil-cooled, replace the oil supply, return, and vent lines and tighten fittings securely.
8. If removed install auto belt tensioner and secure with bolt or bolts. Torque center bolt to 30-38 N·m (22-28 lb·ft) and bracket bolt to 58-73 N·m (43-54 lb·ft) if required.

   NOTICE:
   Failure to properly orient the drive belt when installing it over the pulleys may result in belt damage at engine startup.‪

9. Depending on the application, install the belt(s) carefully over the pulleys on the crankshaft or alternator drive and the drive belt tensioner. If an auto belt tensioner is installed, use a breaker bar with a 3/4 inch drive to rotate the tensioner pulley upward for belt installation. Ensure the grooved and smooth faces of the belt are properly positioned on the pulleys before taking up slack. See Figure "Coach Poly-Vee Belt Installation" .
   

   1. Poly-Vee Belt‪	4. Alternator Pulley‪
   2. Accesory Drive Pulley‪	5. Crankshaft Pulley‪
   3. Belt Adjusting Bracket‪	‪

   Figure 8. Coach Poly-Vee Belt Installation

10. If an auto belt tensioner assembly is not installed, adjust the alternator belt tension. For twin belt-driven alternator refer to "9.2.3.1 Checking Twin-Vee Belt Driven Alternator Belt Tension" . For twin-vee belt-driven 50 DN alternator refer to "9.2.3.1 Checking Twin-Vee Belt Driven Alternator Belt Tension" . For poly-vee belt-driven 50 DN alternator refer to "9.2.3.2 Checking 12-Rib Poly-Vee Belt-Driven 50 DN Alternator Belt Tension" .
11. Torque the alternator-to-mounting bracket bolt and nut and the alternator-to-adjusting rod bracket bolt to 81-95 N·m (60-70 lb·ft).
12. Attach the wires and cables to the alternator. Ensure that each one is correctly installed in the location from which it was removed. Keep all connections clean and tight.

Section 9.2.3.1
Checking Twin-Vee Belt Driven Alternator Belt Tension

The recommended tension for new belts is 556 N (125 lb). However, because new belts lose tension rapidly during the first few minutes of operation, it is important to check the tension after running the engine for 10 to 15 minutes. To check belt tension, use the following procedure: ‪

PERSONAL INJURY ‪
To avoid injury before starting and running the engine, ensure the vehicle is parked on a level surface, parking brake is set, and the wheels are blocked.‪

PERSONAL INJURY ‪
Diesel engine exhaust and some of its constituents are known to the State of California to cause cancer, birth defects, and other reproductive harm.‪ Always start and operate an engine in a well ventilated area. If operating an engine in an enclosed area, vent the exhaust to the outside. Do not modify or tamper with the exhaust system or emission control system.

1. Tension the new drive belts to 556 N (125 lb) using a belt tension tool (J–41251–B) or equivalent.
2. Start and run the engine from 10 to 15 minutes to allow the belts to warm up and seat in the pulley grooves.
3. Stop the engine, and allow it to cool for 10 to 15 minutes.
4. Measure belt tension:
   1. If tension is 445 N (100 lb) or more, no tensioning is required.
   2. If tension is less than 445 N (100 lb), retension the belt to 445 N (100 lb).
5. Check belt tension every 100 hours or 12,000 km (7,500 miles). Refer to "14.6.9 Drive Belts" and retension if necessary.

Section 9.2.3.2
Checking 12-Rib Poly-Vee Belt-Driven 50 DN Alternator Belt Tension

If an auto belt tensioner assembly is installed, no further action is required as long as the belt has been properly positioned in the grooves of the pulleys. If a belt tensioner/support plate assembly is installed, the belt must be tightened to the required value as outline in the following.‪

The recommended tension for new poly-vee belt is 1558 N (350 lb). However, because a new belt loses tension rapidly during the first few minutes of operation, it is important to check the tension after running the engine for 10 to 15 minutes. To check belt tension, use the following procedure:‪

1. Tension the new drive belt to 1558 N (350 lb) using belt tension gage (J–41251–B) or equivalent.
2. Refer to "9.2.3.1 Checking Twin-Vee Belt Driven Alternator Belt Tension" for the exhaust caution before preceding. Start and run the engine for 10 to 15 minutes to allow the belt to warm up and seat in the pulley grooves.
3. Stop the engine, and allow it to cool for 10 to 15 minutes.
4. Measure belt tension:
   1. If tension is 1112 N (250 lb) or more, no further tension is required.
   2. If tension is less than 1112 N (250 lb), adjust belt tension to 1112 N (250 lb).
5. Check belt tension every month, every 100 hours, or every 12,000 km (7,500 miles). Refer to "14.6.9 Drive Belts" and re-tension to 1112 N (250 lb), if necessary.

Section 9.2.3.3
Checking Belt Tension on a Two-Groove Powerband® Alternator Drive Belt

The recommended tension for a new belt is 890 N (200 lb). However, because a new belt loses tension rapidly during the first few minutes of operation, it is important to check the tension after running the engine for 10 to 15 minutes. To check belt tension, use the following procedure:‪

1. Tension the new drive belts to 890 N (200 lb) using appropriate belt tension gage.
2. Refer to "9.2.3.1 Checking Twin-Vee Belt Driven Alternator Belt Tension" for exhaust caution before preceding. Start and run the engine for 10 to 15 minutes to allow the belts to warm up and seat in the pulley grooves.
3. Stop the engine, and allow it to cool for 10 to 15 minutes.
4. Measure belt tension:
   1. If tension is 667 N (150 lb) or more, no tensioning is required.
   2. If tension is less than 667 N (150 lb), adjust the belt tension to 667 N (150 lb).
5. Check belt tension every 100 hours or every 12,000 km (7,500 miles). Refer to "14.6.9 Drive Belts" and re-tension 667 N (150 lb), if necessary.

Section 9.2.3.4
Checking Belt Tension on a 6 – Rib Poly-vee Alternator Drive Belt

The recommended tension for a new belt is 978 N (220 lb). However, because a new belt loses tension rapidly during the first few minutes of operation, it is important to check the tension after running the engine for 10 to 15 minutes. To check belt tension use the following procedure:‪

1. Tension the new drive belts to 978 N (220 lb) using appropriate belt tension gage.
2. Refer to "9.2.3.1 Checking Twin-Vee Belt Driven Alternator Belt Tension" for exhaust caution before preceding. Start and run the engine for 10 to 15 minutes to allow the belts to warm up and seat in the pulley grooves.
3. Stop the engine, and allow it to cool for 10 to 15 minutes.
4. Measure belt tension:
   1. If tension is 800 N (180 lb) or more, no tensioning is required.
   2. If tension is less than 800 N (180 lb), adjust the belt tension to 800 N (180 lb).
5. Check belt tension every 100 hours or every 12, 000 km (7,500 miles). Refer to "14.6.9 Drive Belts" and re-tension to 800 N (180 lb), if necessary.

Section 9.2.3.5
50 DN Alternator Vent Line

Delco 50DN alternators are oil cooled and require an oil supply line from a port on the side of the engine block, an oil drain line from the bottom of the alternator to the oil pan or block, and a vent line to keep the oil within the alternator at an acceptable level and avoid overheating. The original vent line was a No. 4 hose connected between the top of the alternator and a tapped hole in the back of the gear case. Effective June 2000, the former vent line was replaced by a No. 6 braided hose connected between the orifice on top of the alternator and a tapped hole in the mounting plate for the auto belt tensioner assembly. See Figure "Vent Line Installed in Auto Tensioner Mounting Plate" . The larger diameter hose provides improved venting and helps eliminate the potential for vent line plugging, which could lead to insufficient cooling of alternator components and shortened alternator life. ‪

Figure 9. Vent Line Installed in Auto Tensioner Mounting Plate

INSTALLATION OF THE IMPROVED VENT LINE ‪

The improved vent line is installed between the alternator case and the drive belt auto-tensioner mounting plate on the gear case cover. Existing Series 60 engines with auto tensioner assemblies and engines with former manual drive belt tensioner assemblies may be modified to accept the improved vent line. Use the following procedures:‪

PERSONAL INJURY ‪
To avoid injury from hot surfaces, wear protective gloves, or allow engine to cool before removing any component.‪

PERSONAL INJURY ‪
To avoid injury from accidental engine startup while servicing the engine, disconnect/disable the starting system.‪

Installation of Vent Line in Drive Belt Auto Tensioner Assembly Mounting Plate ‪

On engines with current drive belt auto tensioner assemblies, install the improved vent line between the alternator and the tensioner mounting plate as follows:‪

1. With the engine at ambient temperature and cool to the touch, remove and discard the former alternator vent line. Plug the vent line hole at the back of the gear case with a 1/4 in. NPTF square socket head pipe plug.
2. Remove the former vent fitting from the top of the alternator case.
3. Install the 3/8 in. flared to 1/4 in. NPTF, 90 degree elbow into the top of the alternator case.
4. Remove the alternator drive belt. Refer to "9.2.2 Removal of Alternator" .
5. Remove the drive belt auto tensioner assembly from the mounting plate on the gear case cover.
6. Remove the mounting plate from the gear case cover.
7. Drill a 0.425 in. diameter hole on the left side of the mounting plate and thread with a 1/4 in. NPTF - 4FF tap. See Figure "Location of Drilled and Tapped Vent Line Hole in Auto Tensioner Mounting Plate" for hole location.
   

   Figure 10. Location of Drilled and Tapped Vent Line Hole in Auto Tensioner Mounting Plate

8. Clean the plate carefully to remove all drill chaff.
9. Using a new gasket, install the plate onto the gear case cover.
10. Install the auto tensioner assembly onto the mounting plate.
11. Apply DDC®/Loctite® pipe sealant with Teflon® P/N 23509542, or equivalent, to the 3/8 in. flared to 1/4 in. NPTF straight fitting and install into the mounting plate. Attach the improved vent line and tighten securely.

    NOTICE:
    Do not drill the engine lifter bracket to install a hose clip, since this will weaken the bracket.‪

    NOTICE:
    Do not fasten the hose clip to either of the engine lifter bracket mounting bolts. The hose clip must be attached to the bolt on the right side of the lifter bracket to ensure unrestricted air flow through the vent line.‪

12. To prevent sags and low points, secure the vent line with the hose clip. Remove the gear case cover mounting bolt on the right side of the lifter bracket (bolt No. 12 – see Figure "Gear Case Cover Mounting Bolt Locations" ). Attach the hose clip to the bolt, reinstall, and torque the bolt to 58–73 N·m (43–54 lb·ft).
    

    Figure 11. Gear Case Cover Mounting Bolt Locations

13. Install the alternator drive belt. Refer to "9.2.3 Installation of Alternator" .
14. Refer to "9.2.3.1 Checking Twin-Vee Belt Driven Alternator Belt Tension" for the exhaust caution before proceeding. Reconnect starting power, start the engine, and check for proper vent line operation.

Installation of Vent Line in Front Camshaft Cover on Engines with Former Manual Belt Tensioner Assembly ‪

On engines equipped with the former manual belt tensioner assembly, the front camshaft cover is situated behind the tensioner assembly, requiring its removal. Install the improved vent line on these engines as follows:‪

PERSONAL INJURY ‪
To avoid injury from hot surfaces, wear protective gloves, or allow engine to cool before removing any component.‪

PERSONAL INJURY ‪
To avoid injury from accidental engine startup while servicing the engine, disconnect/disable the starting system.‪

1. With the engine at ambient temperature and cool to the touch, remove and discard the former alternator vent line. Plug the vent line hole at the back of the gear case with a 1/4 in. NPTF square socket head pipe plug.
2. Remove the former vent fitting from the top of the alternator case.
3. Install the 3/8 in. flared to 1/4 in. NPTF, 90 degree elbow into the top of the alternator case.
4. Remove the alternator drive belt. Refer to "9.2.2 Removal of Alternator" .
5. Remove the manual belt tensioner assembly from the gear case cover.
6. Remove the front camshaft cover from the gear case cover.
7. The center hole in the cover has a 1/8 in. NPTF thread which must be enlarged. Using a 0.425 in. drill bit, carefully drill out the tapped hole. Thread the hole with a 1/4 in. NPTF - 4FF tap. See Figure "Drilled and Tapped Vent Line Hole in Front Camshaft Cover" .
   

   Figure 12. Drilled and Tapped Vent Line Hole in Front Camshaft Cover

8. Clean the cover carefully to remove all drill chaff.
9. Using a new gasket, install the front camshaft cover onto the gear case cover.
10. Apply Loctite® pipe sealant with Teflon P/N: 23509542, or equivalent, to the 3/8 in. flared to 1/4 in. NPTF straight fitting and install into the cover. Attach the improved vent line and tighten securely.
11. Install the manual belt tensioner assembly.

    NOTICE:
    Do not drill the engine lifter bracket to install a hose clip, since this will weaken the bracket.‪

    NOTICE:
    Do not fasten the hose clip to either of the engine lifter bracket mounting bolts. The hose clip must be attached to the bolt on the right side of the lifter bracket to ensure unrestricted air flow through the vent line.‪

12. To prevent sags and low points, secure the vent line with the hose clip. Remove the gear case cover mounting bolt on the right side of the lifter bracket (bolt No. 12 – see Figure "Gear Case Cover Mounting Bolt Locations" ). Attach the hose clip to the bolt, reinstall, and torque the bolt to 58 –73 N·m (43–54 lb·ft).
13. Install the alternator drive belt. Refer to "9.2.3 Installation of Alternator" .
14. Refer to "9.2.3.1 Checking Twin-Vee Belt Driven Alternator Belt Tension" for the exhaust caution before proceeding. Reconnect starting power, start the engine, and check for proper vent line operation.