Case 680H Backhoe Loader Alternator: Diagnosis, Wiring, and Replacement Guide

[MikePhua]

Introduction
The Case 680H loader/backhoe represents a workhorse in construction applications, typically powered by a 24 V electrical system. A reliable alternator is critical to ensure continuous operation and battery charging while on the job site. Let’s walk through identifying the wiring complexities, diagnosing charging issues, and finding compatible replacement parts.

Common Charging System Confusion
One frequent issue, noted by operators, is that the alternator sometimes has three terminals, but the machine's harness only connects to two. The third — often labeled the "R" (remote) terminal — may have a ring terminal with a broken or missing wire. This can cause the battery to never properly charge, even though basic connections appear intact.


Original Alternator Specs
According to RitchieSpecs, the 680H specification includes:

• Operating Voltage: 24 V
  
• Alternator Output Rating: 40 A
  
  

These values are essential for selecting a proper replacement to ensure adequate charging capacity.

Aftermarket and OEM Alternator Options
Here are viable replacement options based on trusted suppliers:

• RAREELECTRICAL 24 V—Case 680H Compatible
  • Volt: 24 V
    
  • Output: 40 A
    
  • External fan, internal voltage regulator
    
  • Often listed as aftermarket part number 10480060
    
  • Available at retailers like Sears and eBay
    
    
• Alternate New Option (Budget-Friendly)
  • Approx. $132
    
  • Clearly marked for 680H and 336BD diesel models (1980–82)
    
    
• Cat Part Reference (24 V, 75 A)
  • A higher-capacity unit rated at 75 A
    
  • While more powerful, this may exceed the 680H system’s harness capacity
    
    

Troubleshooting and Wiring Tips

• If the "R" terminal is disconnected, remanufacturing this wire may restore proper excitation and charging.
  
• Some reflect that cleaning and securing ground and mounting points resolved no-output issues.
  
• Replacing internal components—voltage regulator and diodes—has restored functionality in many cases without needing a full alternator swap.
  
• Bench-testing or visiting a rebuild shop helps isolate whether a simple internal part swap is sufficient.
  
  

Replacement & Installation Checklist

• Verify Voltage & Amp Rating: Always choose a 24 V unit, ideally 40 A, to match original specifications.
  
• Check Mount Type: Ensure the physical pattern matches — most use external fan and internal regulator configurations.
  
• Examine Wiring Harness:
  • Hook up B+ terminal (battery)
    
  • Connect ground securely via mounting hardware
    
  • If present, reconnect or bypass R (remote) terminal for excitation
    
• Test System: Use a voltmeter—with engine running—to confirm battery voltage rises above ~28 V.
  
• Upgrade Wisely: If replacing with a higher-output unit (like 75 A), ensure wiring and battery capacity can handle it.
  

Additional Notes

• Genuine Cat alternators built to OEM specs are available through self-service kits, including tools and instructions. Great for trusted OEM-level quality.
  
  

Summary Checklist

• Identify alternator terminals: Confirm B+, ground, and R if present
  
• Match original specs: 24 V, ~40 A recommended
  
• Clean mounts: Secure ground path for proper charging
  
• Test before buying: Consider bench testing or professional inspection
  
• Evaluate parts options:
  • RAREELECTRICAL 40 A — budget after-market
    
  • Mid-range new alternator (~$132) for 680H
    
  • Cat self-service kit for OEM quality