Diagnosing Charging System Irregularities on the New Holland 675E

[MikePhua]

The New Holland 675E and Its Electrical Architecture
The New Holland 675E is a mid-sized backhoe loader introduced in the late 1990s as part of New Holland’s push to modernize its construction equipment lineup. Built for versatility in excavation, trenching, and material handling, the 675E features a robust diesel engine, mechanical transmission, and a 12V electrical system designed to support both starting and auxiliary functions. With thousands of units sold globally, it remains a common sight on job sites, especially in municipal and rural operations.
The electrical system on the 675E includes a belt-driven alternator, battery, voltage regulator, instrument cluster, and various sensors. While generally reliable, age and wear can introduce intermittent charging issues that are difficult to diagnose without a methodical approach.
Symptoms of Charging Failure and Instrument Cluster Behavior
A recurring issue reported by operators involves the alternator failing to charge the battery until the throttle is briefly increased. Upon startup, the battery warning light remains illuminated, and the RPM gauge reads zero despite the engine idling. Voltage readings at this stage show:

• Battery terminals: ~12.06V
  
• Alternator output posts: ~11.44V
  
• Ground wire to alternator bracket: ~12.07V
  

Once the throttle is tapped, the RPM gauge activates, the battery light extinguishes, and voltage readings normalize:

• Battery terminals: ~14.12V
  
• Alternator red wire to ground: ~14.26V
  
• Alternator posts: ~7.19V (suggesting internal voltage drop or measurement error)
  

This behavior suggests that the alternator is not fully excited at idle, possibly due to low RPM, poor grounding, or a weak excitation circuit.
Understanding Alternator Excitation and Tachometer Linkage
The alternator in the 675E serves dual roles: charging the battery and providing a signal to the tachometer. The excitation circuit relies on a small current supplied through the instrument cluster to energize the field coil. If the RPM is too low or the excitation current is interrupted, the alternator may not begin charging until engine speed increases.
The tachometer signal is typically derived from the alternator’s stator output. If the alternator is inactive, the tachometer remains at zero. Once the alternator begins producing voltage, the tachometer receives a pulse signal and activates.
In Shanghai, a contractor experienced similar symptoms on a 675E used for trenching. After replacing the alternator and observing no improvement, they traced the issue to a corroded ground strap between the engine block and frame. Cleaning and re-securing the strap restored full charging at idle.
Grounding and Voltage Drop Analysis
Poor grounding is a common cause of intermittent charging. Voltage drop across ground connections can prevent the alternator from receiving proper excitation or returning full current to the battery. To test:

• Measure voltage between alternator case and battery negative terminal
  
• Inspect ground straps for corrosion, fraying, or loose bolts
  
• Use a continuity tester to verify low-resistance paths
  
• Clean contact surfaces and apply dielectric grease
  

Some operators install supplemental ground wires from the alternator bracket directly to the battery negative terminal to ensure consistent current flow.
Alternator Belt Tension and Idle RPM Settings
Another factor is belt tension. A loose belt may slip at low RPM, preventing the alternator from spinning fast enough to generate voltage. Check:

• Belt deflection: Should be less than 1/2 inch under moderate pressure
  
• Pulley alignment: Misaligned pulleys cause uneven wear and slippage
  
• Belt condition: Cracks or glazing reduce grip
  

Additionally, verify that the engine idle speed is set to manufacturer specifications. If idle is too low, the alternator may not reach cut-in speed until the throttle is increased.
Component Replacement and Testing Strategy
If the alternator has been replaced and symptoms persist, consider:

• Testing the voltage regulator (internal or external depending on model)
  
• Inspecting the instrument cluster for faulty warning light circuits
  
• Checking the ignition switch and wiring harness for intermittent faults
  
• Verifying battery health with a load tester and checking for sulfation
  

In Alberta, a fleet manager replaced the alternator on a 675E only to find the issue unresolved. After tracing the excitation wire through the dash, they discovered a broken solder joint on the warning light bulb socket. Repairing the joint restored proper excitation and eliminated the charging delay.
Conclusion
Electrical charging issues on the New Holland 675E often stem from a combination of low idle RPM, poor grounding, and excitation circuit faults. While replacing the alternator may seem like the obvious solution, deeper inspection of the wiring, instrument cluster, and ground paths is often required. With a systematic approach and attention to detail, operators can restore reliable charging performance and ensure the 675E remains a dependable asset on the job site.