Part of the New Holland Repair Manuals.
New Holland covers five Round Baler models (638, 648, 658, 678, 688) in this 464-page repair manual (OEM #87012151), and if you're hunting a New Holland 648 repair manual pdf with real factory depth, this is it. Inside you get complete wiring diagrams for the electrical system, hydraulic schematics covering the tailgate lift and density cylinders, and a full troubleshooting section walking density pressure drops back to their root cause. You also get torque tables, fluid capacity charts, and step-by-step procedures spanning driveline, feeding, pressing, and tying systems. Set net counter roll sensor clearance to 1.5 mm and the 638's tailgate lift orifice to 2.08 mm; other models run 2.6 mm. No more guessing which orifice size fits your baler. This PDF carries bookmarks for every section, so you jump straight to hydraulics or electrical without hunting through 464 pages by hand.
What's Inside This New Holland 638–688 Repair Manual
| System | Pages | Key Topics |
|---|---|---|
| General Information | 15-50 | Foreword, Introduction, Precautionary Statements, Fluid Safety (Handle Fluids Safely, Avoid Heating Near Pressurized Fluid Lines, Use Care Around High-Pressure Fluid Lines) |
| Implement Driveline | 51-108 | PTO, Slide Collar Quick-Disconnect, Drive Shaft and Clutch, Gearbox, Slip Clutches, Special Tools |
| Hydraulic System | 109-142 | Tailgate Lift System, Lockout Valve, Belt Tension System, Density Cylinder(s), Relief Valve Operation, Pickup Lift System |
| Electrical Systems | 143-214 | Components, Adjustments, Electric Components Replacement, Electrical Diagrams, Diagnostic Tests, Connector Repair |
| Product Feeding | 215-238 | Finger Replacement, Cam Bearing Replacement, Slip Clutch Repair, Pickup Removal, Cam Track Replacement, Auger Repair |
| Pressing | 239-360 | Floor Roll, Starter Roll, Apron Rolls, Apron Belts, Sledge Rolls, Take-Up Arm Assembly |
| Tying | 361-464 | Twine Wrapper, Twine Tubes, Twine Knives and Supports, Clutch and Brake Assembly, Cam and Worm Gears, Net Wrapper |
Quick Reference Specifications
| Specification | Value | Page |
|---|---|---|
| 648, 658, 678, 688 | ||
| Net Counter Roll Sensor clearance to magnet | 1.5 mm (1/16″) | p. 149 |
| Tailgate lift system orifice size | 2.6 mm (0.104″) | p. 112 |
| Troubleshooting: Density pressure drop - Possible Causes | Internal leakage., Air in the system., Dirt in the relief valve. | p. 140 |
| Troubleshooting: Density pressure drop - Correction | See internal leakage., Bleed the system., Clean valve. | p. 140 |
| Floor Roll Drive Clutch Slip Torque | 915 - 1125 N∙m (675 - 830 ft lbs) | p. 101 |
| Sledge Roll Drive Clutch Slip Torque | 677 - 767 N∙m (500 - 573 ft lbs) | p. 104 |
| 638 | ||
| Tailgate lift system orifice size | 2.08 mm (0.082″) | p. 111 |
| 638, 648, 658, 678 | ||
| PTO Speed | 540 RPM | p. 46 |
| 688 | ||
| PTO Speed | 540/1000 RPM | p. 48 |
| All Models | ||
| Hydraulic System Minimum Pressure | 11,032 kPa (1800 PSI) | p. 46 |
| Pickup Slip Clutch Torque | 316 N∙m (2800 in. lbs) | p. 46 |
| 648 (silage special), 658, 678, 688 | ||
| Main Drive Slip Clutch Torque (540 RPM) | 1085 - 1627 N∙m (800 - 1200 ft lbs) | p. 98 |
New Holland 638–688 Common Problems This Manual Covers
New Holland 638-688 baler stalls randomly mid-rotation with bale not forming correctly p. 149
Check the net-tension sensor and hydraulic flow valve circuits for loose connectors or contamination. Verify the net counter roll sensor air gap to the magnet measures 1.5 mm (1/16 inch) per the clearance spec on page 149, applicable to 648-688 models. Clean and reseat the connector before condemning the sensor, then retest under load.
Manual Section: Electrical SystemsBale fails to eject after the rotation cycle completes despite normal tying operation p. 140
Test the ejector latch solenoid for continuity and check hydraulic system pressure at the tailgate circuit. Confirm minimum hydraulic pressure meets 11,032 kPa (1800 PSI) per the technical specifications on page 46. Inspect the latch solenoid wiring and the tailgate lift orifice for debris before replacing the solenoid.
Manual Section: Hydraulic SystemSudden hydraulic pressure drop during active baling with erratic, inconsistent bale tension readings p. 140
Check for internal leakage in the main pump seal, air trapped in the hydraulic system, and dirt lodged in the relief valve per the troubleshooting chart on page 140. Bleed the system to clear trapped air, clean the relief valve, and verify minimum system pressure holds at 11,032 kPa (1800 PSI) as listed on page 46.
Manual Section: Hydraulic SystemBale shape alarm triggers repeatedly during normal operation with no visible bale defect
Check the electrical system error code reference for the exact bale density or tailgate sensor fault code. Test sensor wiring continuity and confirm the tailgate sensor clearance measures 3 mm (1/8 inch) per page 149. Clean corroded connector pins and reseat before replacing the sensor assembly.
Manual Section: Electrical SystemsBaler belt shows fraying or lacing damage after several seasons of heavy use p. 136
Inspect the belt for cuts, surface glazing, and lacing pin damage; replace lacing if fasteners are pulling through the material. Check belt tension system pressure, which should hold 166 bar (2400 PSI) on 648-658 models or 148 bar (2150 PSI) on 678-688 models, per page 136. Realign guide rollers to stop recurring edge wear.
Manual Section: Hydraulic SystemFrequently Asked Questions
How to reset the error code on New Holland 648 baler?
To reset an error code on a New Holland 648 baler, press the CLEAR key on the operator's panel. This action will cancel the alarm, whether the error message appears at start-up or while operating the machine.
What are the torque specs for the New Holland 658 gearbox shaft?
For the 540 RPM gearbox, the preload on the input shaft bearings should be set to 0 - 0.5 N⋅m (0 - 4 in. lbs) rolling torque with no end play. Similarly, for the output shaft, install enough shims to obtain a 0 - 0.5 N⋅m (0 - 4 in. lbs) of rolling torque with no end play.
How to reset the baling chamber pressure on New Holland 638?
To adjust the baling chamber pressure, turn the relief valve stem clockwise until it bottoms out. Then, open the tailgate to check the pressure, close it, and adjust the valve stem counterclockwise until the desired pressure is achieved.
How do you fix new Holland 638-688 baler stalls randomly mid-rotation with bale not forming correctly?
Check the net-tension sensor and hydraulic flow valve circuits for loose connectors or contamination. Verify the net counter roll sensor air gap to the magnet measures 1.5 mm (1/16 inch) per the clearance spec on page 149, applicable to 648-688 models. Clean and reseat the connector before condemning the sensor, then retest under load.
Is this New Holland 638 & variants Repair Manual a digital download?
Instant PDF download. You get the full 464-page searchable Repair Manual immediately after payment. Open it on your laptop, tablet, or phone right in the shop.
Can I print specific sections of this New Holland 638 & variants Repair Manual?
The PDF is DRM-free. Print whatever sections you need to take out to the shop. Standard letter or A4 paper works.
Are there hydraulic schematics in this New Holland 638 & variants manual?
Yes, this New Holland 638 & variants Repair Manual includes hydraulic system diagrams, circuit schematics, and component specifications.
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