Troubleshooting and Repairing the Charging System of the Bomag BMP 851

[MikePhua]

The Bomag BMP 851 is a high-performance vibratory plate compactor commonly used in construction and roadwork applications. Known for its powerful engine and efficiency, the BMP 851 is designed to deliver excellent compaction results in tight spaces and on challenging surfaces. However, like any heavy machinery, it requires proper maintenance and attention to ensure optimal performance. One of the critical systems to monitor on the BMP 851 is its charging system, which powers the electrical components of the machine. In this guide, we will explore common issues with the BMP 851's charging system, possible causes, and how to troubleshoot and repair these problems.
Overview of the Charging System in the Bomag BMP 851
The charging system in any heavy equipment is responsible for keeping the battery charged and powering the electrical components when the engine is running. In the Bomag BMP 851, the charging system typically consists of the following components:

• Alternator: The alternator is the primary source of power generation in the charging system. It converts mechanical energy from the engine into electrical energy to charge the battery and power the electrical systems of the machine.
  
• Regulator/Rectifier: The regulator controls the voltage produced by the alternator to prevent overcharging or undercharging the battery. The rectifier converts alternating current (AC) to direct current (DC), which is used by the battery.
  
• Battery: The battery stores the electrical energy generated by the alternator and provides power to the electrical components when the engine is not running.
  
• Wiring and Fuses: The electrical wiring connects the alternator, battery, and other components of the charging system, while fuses protect the system from electrical overloads.
  

A properly functioning charging system ensures that the BMP 851 operates efficiently, with enough power to run its electrical components and start the engine reliably.
Common Charging System Problems in the Bomag BMP 851
Over time, the charging system in the Bomag BMP 851 may experience issues that prevent it from operating correctly. Below are some of the most common problems, their symptoms, and possible causes.
1. Battery Not Charging
One of the most obvious signs of a charging system issue is a battery that doesn't hold a charge or loses power quickly. This can cause the machine to be unable to start or run electrical components effectively.
Symptoms of Battery Charging Issues:

• The battery light on the dashboard remains on.
  
• The machine fails to start even after the battery is charged.
  
• Electrical components, such as lights or controls, malfunction.
  

Possible Causes:

• Faulty alternator: If the alternator is not generating enough power, the battery will not charge.
  
• Broken regulator/rectifier: A malfunctioning regulator can cause overcharging or undercharging, leading to battery failure.
  
• Loose or damaged wiring: Faulty connections or broken wires can interrupt the flow of electricity from the alternator to the battery.
  

Troubleshooting:

• Test the alternator output using a multimeter to check if it is producing the correct voltage (typically between 13.8 and 14.4 volts while the engine is running).
  
• Inspect the regulator/rectifier for any visible signs of damage or wear.
  
• Check all wiring connections for tightness and for any signs of corrosion or wear. Replace damaged wires as necessary.
  

2. Alternator Not Producing Voltage
If the alternator is not producing voltage, the machine will rely on the battery for power, leading to a dead battery after a short period.
Symptoms of Alternator Failure:

• The battery drains quickly even after being charged.
  
• The engine may start slowly or not at all, especially if the battery is dead.
  
• The machine operates for a short time and then dies once the battery is depleted.
  

Possible Causes:

• Worn alternator brushes: The alternator brushes wear out over time and can cause a failure in the alternator’s ability to generate voltage.
  
• Damaged alternator belt: If the alternator belt is worn or broken, it may not be turning the alternator properly, preventing it from generating power.
  
• Internal alternator damage: Internal components like the stator or rotor can fail, causing the alternator to stop working.
  

Troubleshooting:

• Check the alternator belt for any signs of wear or damage and replace it if necessary.
  
• Use a multimeter to measure the output voltage of the alternator while the engine is running. If the output is too low or nonexistent, the alternator likely needs to be replaced.
  
• Inspect the alternator brushes for wear and replace them if they are excessively worn down.
  

3. Overcharging the Battery
An overcharged battery can be just as problematic as an undercharged battery. Overcharging can cause the battery to overheat, which can lead to fluid loss, damage to internal components, and ultimately battery failure.
Symptoms of Overcharging:

• The battery fluid level decreases rapidly.
  
• The battery becomes excessively hot to the touch.
  
• The battery light on the dashboard turns on after a period of operation.
  

Possible Causes:

• Faulty voltage regulator: If the voltage regulator is malfunctioning, it may allow too much voltage to pass through to the battery, leading to overcharging.
  
• Incorrect alternator output: The alternator may be producing more voltage than necessary due to an internal fault.
  

Troubleshooting:

• Test the voltage output of the alternator and the regulator using a multimeter. The voltage should typically stay within the 13.8 to 14.4-volt range.
  
• Inspect the voltage regulator for signs of failure, such as burned-out components or loose connections.
  
• Replace the regulator if it is found to be defective.
  

4. Electrical Shorts or Malfunctions
Electrical shorts or wiring malfunctions can prevent the charging system from functioning properly. A short circuit or damaged wiring can interrupt the flow of electricity, leading to charging issues.
Symptoms of Electrical Shorts:

• Fuses constantly blow, even after replacement.
  
• Electrical components fail to work correctly or intermittently.
  
• The battery drains even with a functioning alternator.
  

Possible Causes:

• Damaged or frayed wiring: Over time, wires can become frayed or worn, causing shorts or broken connections.
  
• Faulty fuses: Fuses are designed to protect the charging system from electrical overloads. If they blow frequently, it may indicate an underlying wiring problem or an overloaded circuit.
  

Troubleshooting:

• Inspect all wiring for signs of wear, fraying, or damage. Pay close attention to areas where wires are exposed to excessive heat or movement.
  
• Check fuses for continuity and replace any blown fuses with the appropriate amperage.
  
• Use a multimeter to check for shorts in the wiring by testing continuity between the positive and negative terminals of the battery.
  

Preventative Maintenance for the Bomag BMP 851 Charging System
Preventative maintenance is key to ensuring the longevity and reliability of the charging system in your Bomag BMP 851. Here are some tips:

• Regularly inspect the alternator belt for wear and replace it as needed.
  
• Check the battery fluid levels and top them off with distilled water if necessary.
  
• Test the charging system at regular intervals, especially if the machine is not starting properly or if the battery seems to be draining too quickly.
  
• Clean the battery terminals and ensure that the battery is properly secured in its compartment.
  
• Replace the regulator and alternator as part of a proactive maintenance routine if they show signs of wear or inefficiency.
  

Conclusion
The charging system is an essential component of the Bomag BMP 851 backhoe, ensuring that the battery stays charged and that the machine’s electrical systems operate smoothly. Common issues such as alternator failure, battery charging problems, and overcharging can disrupt the operation of the machine. However, with proper troubleshooting and maintenance, these issues can often be resolved quickly and effectively.
By regularly inspecting the charging system components, such as the alternator, regulator, and wiring, you can keep your BMP 851 in peak condition and avoid costly repairs down the line. With a little care and attention, the charging system of your Bomag BMP 851 will continue to function efficiently for years to come.