Part of the John Deere Repair Manuals.
Rebuilding a charging system on an older Deere machine? This 576-page John Deere Alternators Technical Manual PDF (CTM77) walks through alternator and starter motor repair for every OEM supplier: Delco-Remy 10SI, 12SI, 15SI and 21SI, Motorola 8E-Series, plus Niehoff, Denso, Bosch, Valeo, Magneton, Leece-Neville, Prestolite and Iskra units. You get theory-of-operation sections for each family, exploded views for teardown and reassembly, a seven-step electrical test procedure, and troubleshooting charts for charging and starting circuit failures. Page after page of repair specifications backs up every job on your bench. Torque the regulator mounting screws to 2 N-m (20 lb-in.) and the drive end bearing retainer plate cap screws to 3.0 N-m (26 lb-in.); a good ground should read 0.0 to 0.5 volts. No more swapping parts to guess at a bad diode trio. Bookmarked PDF opens on any device; search any spec by keyword and get wrenching.
What's Inside This John Deere Alternators & Starter Motors (all OEM units) Manual
| System | Pages | Key Topics |
|---|---|---|
| Introduction and Safety Information | 9-30 | Safety Precautions, How to Use This Component Technical Manual, Unified Inch and Metric Torque Values, General Charging and Starting Circuit Terms |
| Delco-Remy Alternators | 31-72 | Delco-Remy Alternator Theory of Operation, Delco-Remy 10SI, 12SI and 15SI Alternator Repair, Delco-Remy 21SI Alternator Repair |
| Motorola Alternators | 73-172 | Motorola Alternator Theory of Operation, Motorola 8E-Series Alternator Repair, Motorola Hc-, Ma-, MR-Series Alternator Repair, Motorola A-, Ra-, 8AR-Series Alternator Repair |
| Niehoff Alternators | 173-224 | Niehoff Alternator Theory of Operation, Niehoff 12-Volt, 110-Amp Alternator Repair, Niehoff 24-Volt, 50-Amp Alternator Repair |
| Denso Alternators | 225-264 | Denso Alternator Theory of Operation, Denso Alternator with Add-On Regulator Repair, Denso Alternator with Built-In Regulator Repair |
| Robert Bosch Alternators | 265-288 | Robert Bosch Alternator Theory of Operation, Robert Bosch Alternator Repair |
| Valeo Alternators | 289-318 | Valeo Alternator Theory of Operation, Valeo Alternator Repair, Valeo A13N-Series Alternator Repair |
| Magneton Alternators | 319-336 | Magneton Alternator Theory of Operation, Magneton Alternator Repair |
| Leece-Neville Alternators | 337-346 | Alternator Operation, Repair Specifications, Charging System Failure, Alternator Troubleshooting, Diode Trio Test, Adjust Regulator |
| Prestolite Alternators | 347-354 | Alternator Operation, Charging Circuit Test Specifications, Repair Alternator, Charging System Failure, Alternator Troubleshooting, Test Alternator |
| Delco-Remy Starter Motors | 355-444 | Starting Circuit Theory of Operation, Starter Motor Repair Specifications, Diagnosing Starter Motor Malfunctions, Disassemble Starter Motor, Inspect Armature |
| John Deere/Denso Starter Motors | 445-508 | Starting Circuit Theory of Operation, Starter Motor Repair Specifications, Test Starter Motor Before Disassembly, Diagnose No-Load Test, Inspect Armature, Assemble Starter Motor |
| Robert Bosch Starter Motors | 509-530 | Starting Circuit Theory of Operation, Starter Motor Repair Specifications, Diagnosing Starter Motor Malfunctions, Robert Bosch Starter Motor Exploded View, Testing Armature |
| Iskra Starter Motors | 531-552 | Starting Circuit Theory of Operation, Starter Motor Repair Specifications, Exploded View of Iskra Starter Motor, Troubleshooting, Disassembly of Starter Motor |
| Valeo Starter Motors | 553-570 | Starting Circuit Theory of Operation, Starter Motor Repair Specifications, Exploded View of Starter Motor, Disassembly of Starter Motor, Testing Armature |
Quick Reference Specifications
| Specification | Value | Page |
|---|---|---|
| Normal indicated voltage at a ground connection | 0.0 to 0.5 volts | p. 23 |
| Alternator bearings lubricant | Delco-Remy Lubricant No. 1948791 | p. 36 |
| Regulator Mounting Screws Torque | 2 N•m (20 lb-in.) | p. 53 |
| Drive End Bearing Retainer Plate Cap Screws Torque | 3.0 N•m (26 lb-in.) | p. 54 |
| Slip Ring-to-Shaft - Torque | 40 N·m (30 lb-ft) | p. 88 |
| Loose belts | Loose belts | p. 352 |
| Unified Inch Bolt and Cap Screw Torque (Lubricated, Grade 8, 1/2 inch) | 120 N•m (88 lb-ft) | p. 19 |
| Metric Bolt and Cap Screw Torque (Lubricated, Class 12.9, M10) | 75 N•m (55 lb-ft) | p. 20 |
| Delco-Remy Model 12SI Alternator Pulley Nut Torque | 100 N•m (75 lb-ft) | p. 38 |
John Deere Alternators & Starter Motors (all OEM units) Common Problems This Manual Covers
John Deere alternator not charging, battery warning light stays on after engine start, voltage below 13.5V
Check drive belt tension before condemning the alternator. Test system voltage at 1,500 RPM; below 13.5 volts means undercharging. Run the alternator output test and diode trio test starting on page 342. Measure voltage drop at every ground connection; anything above 0.5 volts points to a bad ground, not the alternator.
Manual Section: Alternator Troubleshooting (Leece-Neville) p. 342Battery overcharging above 15.0 volts with blown bulbs and fuses even after installing a new battery
Test regulated voltage with the engine warm. At 29°C (85°F) ambient the regulator should hold 13.8 to 14.9 volts, per the temperature chart on page 53. Anything holding above 15.0 volts, replace the regulator. Torque the new regulator mounting screws to 2 N•m (20 lb-in.) and retest before reconnecting accessories.
Manual Section: Delco-Remy Alternators p. 53Grinding or whining noise from alternator that gets louder with engine speed, bearings suspected
Remove the alternator and spin the rotor by hand; any roughness or side play means the bearings are done. Replace both bearings, pack the drive end bearing with Delco-Remy Lubricant No. 1948791, and torque the retainer plate cap screws to 3.0 N•m (26 lb-in.) per page 54. Check pulley alignment before reinstalling the belt.
Manual Section: Delco-Remy Alternators p. 54Starter cranks slowly or clicks from the solenoid without engaging in cold weather
Clean and tighten the battery terminals first; corrosion causes most slow cranking complaints. Load test the battery, then run the no-load current draw test using the procedures. High current draw with low speed points to worn bushings or a dragging armature. Replace brush springs testing below 990 gram force (35 ounce-force).
Manual Section: Diagnosing Starter Motor Malfunctions (Delco-Remy 10/20/22/25/27/28MT)New alternator installed but battery still runs down, belt squeals on cold morning starts
Check belt tension before blaming the new unit; loose belts appear in the troubleshooting chart on page 352 as a leading cause of low output. Adjust tension or replace a glazed, cracked belt. Then verify system voltage climbs above 13.5 volts at 1,500 RPM with all connections clean and tight.
Manual Section: Prestolite Alternators p. 352Frequently Asked Questions
How to reset John Deere alternator charging fault?
The manual describes troubleshooting steps for charging faults but does not provide a general "reset" procedure. For Niehoff 12-Volt, 110-Amp and 24-Volt, 50-Amp alternators, a "Re-Establish Magnetic Field" procedure is available if the magnetic field has not been established, which involves using a jumper wire. This procedure takes only a few seconds. p. 205
What are the torque specs for John Deere alternator mounting bolts?
The manual provides torque specifications for internal assembly components of various alternators, such as housing through bolts and pulley nuts, but it does not list specific torque values for mounting the alternator to the engine. p. 298
What does alternator error code mean on John Deere dashboard?
The manual discusses symptoms related to the "alternator indicator light" (e.g., staying off or on) and their potential causes, but it does not provide information on specific "alternator error codes" or "fault codes" that might be displayed on a John Deere dashboard. p. 328
Why is my John Deere alternator not producing 14.2-14.5 volts?
If a Leece-Neville alternator is not producing the specified voltage, it indicates an undercharge condition. For example, if the voltage is lower than the specified 13.5—14.2 volts for a Motorola 8E-Series alternator, the alternator is defective and should be replaced. This could be due to a defective diode trio, damaged or worn brushes/slip rings, poor connections, or an improperly adjusted regulator. p. 344
How to excite a John Deere alternator with a jumper wire?
For Niehoff 12-Volt, 110-Amp and 24-Volt, 50-Amp alternators, the magnetic field can be re-established by connecting the alternator ground stud (A) to the field coil through the inspection hole (B) with a jumper wire. This procedure should be performed while the alternator output is connected to the battery positive post and alternator ground to the battery negative post, and it takes only a few seconds. p. 205
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