Introduction
The Caterpillar 931B Track Loader, a robust machine introduced in the late 1970s, is renowned for its versatility and reliability in various construction and agricultural applications. However, like all heavy machinery, it requires maintenance and occasional repairs. One common task is the removal and replacement of hydraulic hoses, which can become worn or damaged over time. Understanding the proper procedures for this task is essential to ensure the loader's continued performance and safety.
Understanding the Hydraulic System
The hydraulic system of the 931B is integral to its operation, powering components such as the lift arms, bucket, and steering. The system comprises hydraulic pumps, cylinders, valves, and hoses that work in unison to perform various functions. Hydraulic hoses, typically made of durable rubber or composite materials, transport pressurized fluid to actuate these components. Over time, these hoses can deteriorate due to factors like abrasion, exposure to extreme temperatures, or chemical exposure, necessitating replacement.
Preparation for Hose Removal
Before attempting to remove any hydraulic hose, it's crucial to take the following preparatory steps:

1. Depressurize the Hydraulic System: Ensure that the hydraulic system is not under pressure to prevent accidental fluid discharge. This can be achieved by turning off the engine and operating all hydraulic functions to relieve pressure.
   
2. Identify the Hose to Be Replaced: Clearly mark the hose connections to avoid confusion during reinstallation. It's advisable to take photographs or make diagrams of the hose routing and connections.
   
3. Gather Necessary Tools: Equip yourself with the appropriate tools, including flare nut wrenches, adjustable wrenches, and safety gloves. Using the correct tools will prevent damage to fittings and ensure a secure connection during reassembly.
   

1. Locate the Hose Connections: Depending on the specific hose, it may be routed under the floorboard or near the lift cylinder mount. For example, hoses under the left floorboard connecting the loader boom cylinder to the steel lines are typically around 30 inches in length .
   
2. Loosen the Hose Fittings: Using a flare nut wrench, carefully loosen the fittings at both ends of the hose. Applying penetrating oil to the fittings beforehand can help ease the removal process.
   
3. Remove the Hose: Once the fittings are loosened, remove the hose from its routing. Be cautious of any residual hydraulic fluid that may leak out during this process.
   
4. Inspect Associated Components: While the hose is removed, it's an opportune time to inspect related components such as fittings, brackets, and other hoses for wear or damage.
   

1. Install the New Hose: Position the new hose in the same routing as the old one, ensuring it does not interfere with other components or moving parts.
   
2. Connect the Fittings: Attach the fittings to the hose ends, ensuring they are tightened securely but not over-torqued, which could damage the fittings or hose.
   
3. Check for Leaks: After reinstallation, start the engine and operate the hydraulic functions to check for any leaks at the hose connections. If leaks are detected, tighten the fittings as necessary.
   

• Always wear appropriate personal protective equipment (PPE), including safety gloves and eye protection, when working with hydraulic systems.
  
• Dispose of any used hydraulic fluid in accordance with local environmental regulations.
  
• If uncertain about any step in the process, consult the Caterpillar 931B service manual or seek assistance from a qualified technician.
  

The Rise of Michigan Loaders in Postwar Construction
The Michigan 125A wheel loader was part of a pivotal era in American heavy equipment manufacturing. Built by Clark Equipment Company, which originated in Michigan in the early 20th century, the 125A emerged during the 1960s and 1970s when infrastructure expansion and industrial growth demanded rugged, high-capacity machines. Clark’s Michigan line became synonymous with reliability and brute strength, especially in quarrying, logging, and bulk material handling.
Terminology annotation:
- Wheel loader: A heavy machine equipped with a front-mounted bucket used for scooping, lifting, and transporting loose materials.
- Articulated frame: A chassis design that allows the front and rear halves of the machine to pivot, improving maneuverability.
- Planetary drive axle: A gear system within the axle that multiplies torque and reduces stress on drivetrain components.
Core Specifications and Mechanical Design
The Michigan 125A was typically powered by a Detroit Diesel 6V-71 engine, a two-stroke V6 known for its distinctive sound and high torque output. The loader featured a four-wheel-drive layout, planetary axles, and a torque converter transmission that allowed smooth operation under load.
Key parameters:

• Engine: Detroit Diesel 6V-71, ~238 hp
  
• Operating weight: ~40,000 lbs
  
• Bucket capacity: 4.5 to 5.5 cubic yards
  
• Transmission: Clark powershift with multiple forward and reverse speeds
  
• Tires: 23.5x25 bias-ply or radial, depending on configuration
  
• Hydraulic system: Open-center with gear pump, ~50 GPM flow rate
  

• Hydraulic leaks from aged hoses and fittings
  
• Transmission hesitation due to worn clutch packs
  
• Steering drift from worn pins or cylinder seals
  
• Electrical faults in starter solenoids or lighting circuits
  

• Replace hydraulic hoses every 3,000 hours or 5 years
  
• Flush transmission fluid annually and inspect filter screens
  
• Rebuild steering cylinders with OEM seal kits
  
• Upgrade wiring harness with modern connectors and relays
  

• Install LED work lights for improved visibility
  
• Retrofit cab with sound insulation and suspension seat
  
• Add auxiliary hydraulic circuit for grapple or snow blade
  
• Replace analog gauges with digital cluster for diagnostics
  

Introduction
Excavators are versatile machines used in various construction and mining applications. To optimize performance and fuel efficiency, modern excavators are equipped with selectable power modes. These modes adjust the engine speed and hydraulic flow to match the demands of different tasks. Understanding how to utilize these modes effectively can lead to significant improvements in productivity and cost savings.
Understanding Excavator Hydraulics
Excavators rely on hydraulic systems to perform tasks such as digging, lifting, and rotating. The hydraulic system operates by using an engine-powered pump to pressurize fluid, which is then directed through valves and hoses to cylinders and motors. The key components of an excavator's hydraulic system include:

• Hydraulic Pump: Converts mechanical energy from the engine into hydraulic energy.
  
• Valves: Direct the flow of hydraulic fluid to various actuators.
  
• Cylinders and Motors: Perform the physical work, such as moving the boom or rotating the cab.
  

• Power Mode (P Mode): Provides maximum engine speed and hydraulic flow, suitable for heavy-duty tasks like digging through hard soil or lifting heavy loads.
  
• Smart Mode: Automatically adjusts engine speed and hydraulic flow based on the load and operator inputs, balancing power and fuel efficiency.
  
• Eco Mode: Reduces engine speed to a constant level, minimizing fuel consumption for lighter tasks.
  

• Fuel Efficiency: By matching engine speed and hydraulic flow to the task, fuel consumption can be optimized.
  
• Extended Equipment Life: Operating in the correct mode reduces strain on components, leading to longer service life.
  
• Cost Savings: Improved fuel efficiency and reduced maintenance costs contribute to overall savings.
  

The D4G XL and Its Electrical System Design
The Caterpillar D4G XL is a mid-size crawler dozer introduced in the early 2000s as part of CAT’s G-series lineup. Designed for grading, site prep, and light earthmoving, the D4G XL features a turbocharged diesel engine, hydrostatic transmission, and electronically integrated control systems. Caterpillar, founded in 1925, has long emphasized durability and modular serviceability, and the D4G XL reflects this with its compartmentalized wiring harnesses, sealed connectors, and diagnostic-friendly layout.
The electrical system on the D4G XL includes multiple safety interlocks, a centralized fuse block, and an Engine Control Module (ECM) that governs ignition, fuel delivery, and system readiness. When the machine fails to start with no dash lights, horn, or accessory power, the fault typically lies in the primary power distribution or a failed safety circuit.
Terminology annotation:
- ECM (Engine Control Module): A microprocessor-based unit that manages engine functions, including ignition timing and fuel injection.
- Fuse block: A panel containing fuses that protect electrical circuits from overload.
- Safety interlock: A system that prevents engine start unless specific conditions are met, such as neutral gear or operator presence.
Symptoms and Initial Observations
Operators encountering a no-start condition on the D4G XL often report:

• No dash illumination when the key is turned
  
• No horn, lights, or accessory function
  
• Batteries test fine but no power reaches the ignition
  
• Temporary restoration of power after manipulating connectors
  

• Clean all connectors with electrical contact cleaner
  
• Apply dielectric grease to prevent future corrosion
  
• Inspect wire crimps and solder joints for fatigue
  
• Replace damaged connectors with sealed weatherproof types
  

• Remove and clean battery terminals
  
• Inspect ground strap from frame to engine block
  
• Use a multimeter to check voltage drop across connections
  
• Replace cables showing signs of swelling or heat damage
  

• Trace all spliced wires and verify proper insulation
  
• Use heat-shrink tubing and soldered joints for repairs
  
• Confirm ECM mounting and grounding integrity
  
• Check ECM connector pins for corrosion or misalignment
  

• Locate and test all push-button breakers for continuity
  
• Swap relays with known-good units to isolate faults
  
• Feel for warm wires or components indicating a short
  
• Use voltage tracing from battery to ignition switch
  

• Inspect and clean connectors every 250 hours
  
• Replace fuses and relays every 1,000 hours or during major service
  
• Use sealed connectors in high-moisture environments
  
• Label wiring modifications and document changes
  
• Install battery disconnect switches to prevent parasitic drain
  

Introduction
Caterpillar Inc., a global leader in heavy equipment manufacturing, has built a reputation for producing durable and high-performance machinery. However, like all mechanical systems, their equipment requires maintenance and occasional part replacements. Understanding the options available for replacement parts—whether genuine OEM parts or aftermarket alternatives—is crucial for maintaining equipment performance and longevity.
Caterpillar's Legacy and Equipment Overview
Founded in 1925, Caterpillar Inc. emerged from the merger of the C.L. Best Tractor Company and Holt Manufacturing Company. Over the decades, the company has become synonymous with heavy machinery, offering a wide range of equipment from bulldozers and excavators to generators and engines. Their products are renowned for their robustness and reliability, making them a preferred choice in construction, mining, and agricultural sectors.
Understanding Replacement Parts
Replacement parts are components used to replace damaged or worn-out parts in machinery. They are essential for restoring equipment to its optimal operating condition. These parts can be broadly categorized into:

• OEM (Original Equipment Manufacturer) Parts: These are parts produced by the original manufacturer, in this case, Caterpillar. They are designed to meet the exact specifications of the original components, ensuring compatibility and performance.
  
• Aftermarket Parts: These are parts produced by third-party manufacturers. They are designed to fit and function like OEM parts but may vary in quality, price, and availability.
  

1. Compatibility: OEM parts are designed specifically for Caterpillar equipment, ensuring a perfect fit and optimal performance.
   
2. Quality Assurance: Caterpillar's stringent manufacturing standards ensure that OEM parts meet high-quality benchmarks, leading to enhanced durability and reliability.
   
3. Warranty Protection: Using OEM parts helps maintain the validity of equipment warranties, as many manufacturers require the use of genuine parts for warranty coverage.
   
4. Longevity: OEM parts are engineered to last, reducing the frequency of replacements and associated downtime.
   

1. Cost-Effectiveness: Aftermarket parts are often more affordable than OEM parts, providing budget-friendly options for repairs and maintenance.
   
2. Availability: With numerous manufacturers producing aftermarket parts, they can be more readily available, potentially reducing lead times for repairs.
   
3. Varied Quality: The quality of aftermarket parts can vary significantly between manufacturers. It's essential to research and select reputable suppliers to ensure reliability.
   
4. Compatibility Risks: While designed to fit, some aftermarket parts may not meet the exact specifications of OEM parts, potentially leading to performance issues.
   

• Equipment Age: For newer equipment still under warranty, OEM parts are recommended to maintain warranty coverage. For older equipment, aftermarket parts can be a cost-effective solution.
  
• Critical Components: For vital systems like engines and hydraulics, OEM parts are advisable to ensure optimal performance and safety.
  
• Budget Constraints: If cost is a significant concern, reputable aftermarket parts can offer savings without compromising quality.
  

What a Pilot Valve Does and Why It Matters
Pilot valves are small but essential components in hydraulic systems, acting as low-pressure control devices that regulate the operation of larger main valves. In heavy machinery such as excavators, dozers, and loaders, pilot valves translate operator input—typically from joysticks or pedals—into directional flow signals that activate high-pressure hydraulic circuits. Without a functioning pilot valve, even the most powerful hydraulic pump becomes inert.
Terminology annotation:
- Pilot valve: A low-pressure control valve that directs fluid to actuate a larger main valve.
- Main spool valve: The primary valve that controls high-pressure flow to actuators like cylinders or motors.
- Hydraulic actuation: The process of using pressurized fluid to move mechanical components.
Common Symptoms of Pilot Valve Failure
When a pilot valve begins to fail or malfunctions, the machine may exhibit the following behaviors:

• Joystick or pedal inputs result in delayed or no response
  
• Hydraulic functions operate intermittently or erratically
  
• Machine starts but cannot move boom, arm, or bucket
  
• Audible hissing or vibration from control lines
  
• Pilot pressure readings drop below specification
  

• Disconnect electrical connectors and label them for reassembly
  
• Remove hydraulic lines and cap ports to prevent contamination
  
• Extract the valve body and inspect for scoring or corrosion
  
• Disassemble the spool and spring assembly
  
• Replace all seals, O-rings, and centering components
  
• Clean internal passages with solvent and compressed air
  

• Use OEM or high-quality aftermarket seal kits
  
• Avoid abrasive cleaning methods that damage spool surfaces
  
• Test valve function on a bench before reinstalling
  
• Flush pilot lines and filters before reconnecting
  

• Identify valve by casting number and machine model
  
• Measure port sizes and thread types
  
• Confirm voltage and connector type for solenoid models
  
• Ask suppliers for flow and pressure ratings
  
• Consider rebuilding if replacement is unavailable
  

• Replace hydraulic fluid every 500–1,000 hours
  
• Use fine-micron filters to prevent contamination
  
• Inspect electrical connectors for corrosion quarterly
  
• Lubricate control linkages and pedal pivots monthly
  
• Avoid excessive joystick force that stresses valve components
  

Introduction
The John Deere 310B backhoe loader, a staple in construction and agricultural operations, is renowned for its durability and versatility. However, like any complex machine, it is susceptible to hydraulic issues that can impede performance. This article delves into common hydraulic problems encountered with the 310B, offering insights into their causes, diagnostic procedures, and potential solutions.
Common Hydraulic Issues

1. Slow or Jerky Hydraulic Functions
   Operators may notice that the loader or backhoe operates slowly or exhibits jerky movements. This symptom often indicates a lack of hydraulic pressure or flow. Potential causes include:
   • Low Hydraulic Fluid Levels: Insufficient fluid can lead to cavitation, causing erratic hydraulic function.
     
   • Clogged Filters: Obstructed filters can restrict fluid flow, reducing system efficiency.
     
   • Contaminated Fluid: Debris or degraded fluid can impair pump performance and valve operation.
     
2. Unusual Noises
   Hearing whining or squealing sounds from the hydraulic system, especially during startup or under load, suggests possible air in the system or a failing pump. Air can enter through:
   • Loose or Damaged Seals: Allowing air to infiltrate the hydraulic lines.
     
   • Improperly Seated Filters: Failing to ensure proper seating can create air entry points.
     
3. Inconsistent Steering
   If the steering becomes unresponsive or exhibits inconsistent behavior, it may be due to:
   • Priority Valve Malfunctions: The priority valve directs hydraulic flow to essential functions like steering. A malfunction can divert flow away from the steering system.
     
   • Pressure Control Valve Issues: A faulty valve can disrupt the balance of hydraulic pressure, affecting steering performance.
     

1. Check Hydraulic Fluid Levels
   Ensure the hydraulic fluid is at the recommended level. Low fluid can cause cavitation and pump damage.
   
2. Inspect Filters and Screens
   • Hydraulic Filters: Replace if clogged or contaminated.
     
   • Transmission Sump Screen: Clean to remove debris that could obstruct fluid flow.
     
3. Test Hydraulic Pressures
   Using a pressure gauge, measure the system's hydraulic pressures:
   • Standby Pressure: Should be approximately 200 psi.
     
   • Main Pressure: Typically around 2,000 psi.
     
   Deviations from these values can indicate pump issues or pressure control valve malfunctions.
   
4. Examine for Air in the System
   • Bleed the System: Operate all hydraulic functions to expel trapped air.
     
   • Check for Leaks: Inspect hoses and connections for signs of air ingress.
     
5. Assess the Priority Valve
   • Location: Typically found near the transmission case.
     
   • Function: Ensures steering receives adequate hydraulic flow.
     
   • Inspection: Check for wear, damage, or debris that could impede function.
     

1. Replace or Clean Filters
   Regular maintenance of filters ensures unobstructed fluid flow and prevents contaminants from entering the system.
   
2. Repair or Replace Faulty Valves
   • Pressure Control Valve: If malfunctioning, it may need repair or replacement.
     
   • Priority Valve: Ensure it is free from debris and operates smoothly.
     
3. Flush the Hydraulic System
   If contamination is suspected, flushing the system with a compatible solvent can remove debris and restore performance.
   
4. Replace the Hydraulic Pump
   If diagnostics point to pump failure, replacing it with a genuine John Deere part ensures compatibility and reliability.
   

The 580C and Its Hydraulic Legacy
The Case 580C backhoe loader was introduced in the late 1970s as part of Case’s evolution in compact construction machinery. With a reputation for reliability and mechanical simplicity, the 580C became a staple on job sites and farms across North America. Powered by a 3.4L diesel engine and equipped with open-center hydraulics, the machine offered straightforward serviceability and robust performance in digging, trenching, and material handling.
Case Corporation, founded in 1842, had by the 1980s become a global leader in agricultural and construction equipment. The 580C was one of its most successful models, with tens of thousands sold worldwide. Its backhoe valve bank—a cluster of spool valves controlling boom, dipper, bucket, and swing functions—was designed for durability but often requires refurbishment after decades of use.
Terminology annotation:
- Valve bank: A group of hydraulic control valves mounted together to manage multiple functions.
- Spool valve: A cylindrical sliding component inside a valve body that directs fluid flow based on operator input.
- Open-center hydraulics: A system where fluid circulates continuously until a valve is actuated, offering simplicity and low cost.
Symptoms of Valve Bank Wear and Failure
After years of operation, the backhoe valve bank may exhibit the following issues:

• Sticky or slow lever response
  
• Internal leakage causing drift in boom or bucket
  
• External leaks from seals and O-rings
  
• Uneven flow or jerky movement during operation
  
• Difficulty feathering controls for fine grading
  

• Remove control levers and linkage arms
  
• Disconnect hydraulic lines and cap ports to prevent contamination
  
• Extract spools and inspect for wear or galling
  
• Clean valve bores with lint-free cloth and solvent
  
• Replace all O-rings, backup rings, and seals with OEM-grade kits
  
• Reassemble with proper torque and alignment
  

• Use a seal kit matched to the valve casting number
  
• Polish spool surfaces with fine emery cloth if scoring is light
  
• Replace detent balls and springs if lever retention is weak
  
• Flush hydraulic system before reconnecting to prevent debris ingress
  

• Replace hydraulic fluid every 500 hours or annually
  
• Clean breather caps and inspect filters quarterly
  
• Lubricate control linkages monthly
  
• Avoid pressure washing near valve bodies to prevent water ingress
  
• Use fluid sampling kits to detect early contamination
  

• Ensure flow and pressure ratings match the original system
  
• Modify control tower to accommodate new levers or joysticks
  
• Install proportional valves for smoother feathering
  
• Add auxiliary circuits for thumbs or hydraulic hammers
  

Introduction
Steel tracks from bulldozers and other tracked heavy equipment are engineered for durability and performance in challenging terrains. However, once these tracks reach the end of their service life, they often end up discarded. Instead of sending them to scrap, consider repurposing these robust components. This article explores various practical and creative ways to give new life to old dozer steel tracks.
Understanding Steel Tracks
Steel tracks are integral to the undercarriage system of tracked vehicles. Comprising components like track links, shoes, rollers, and sprockets, these tracks are designed to distribute the vehicle's weight evenly, providing stability and mobility across soft or uneven ground. The durability of steel tracks makes them suitable for heavy-duty applications, but when they become worn or obsolete, their potential for reuse is often overlooked.
Practical Applications

1. Driveway Edging and Landscaping Borders
   • Description: Utilize the track links or shoes to create durable borders for driveways, garden paths, or flower beds.
     
   • Benefits: These steel components are weather-resistant and can withstand the elements, providing long-lasting edging solutions.
     
2. Fencing and Agricultural Structures
   • Description: Repurpose track links to construct sturdy fences or gates for agricultural purposes.
     
   • Benefits: The strength of steel ensures that these structures can endure harsh conditions and provide security for livestock or property.
     
3. Road Maintenance Tools
   • Description: Use the steel tracks as drag mats for maintaining dirt or gravel roads.
     
   • Benefits: Their weight and design make them effective in smoothing out rough surfaces and filling in ruts.
     
4. Heavy-Duty Shelving and Racking Systems
   • Description: Incorporate track links into the design of industrial shelving units or racking systems.
     
   • Benefits: The robust nature of steel tracks ensures that these storage solutions can bear heavy loads.
     

1. Outdoor Furniture
   • Description: Transform track links into unique pieces of outdoor furniture, such as benches or tables.
     
   • Example: A director's chair crafted from recycled bulldozer tracks and steel gears showcases the potential for artistic expression using industrial materials.
     
2. Sculptures and Yard Art
   • Description: Weld track links together to create sculptures or decorative yard art.
     
   • Benefits: These creations can serve as focal points in gardens or public spaces, blending industrial aesthetics with artistic design.
     
3. Custom Welding Tables
   • Description: Utilize sprockets to construct rotating welding tables.
     
   • Benefits: The durability and functionality of these tables can enhance welding operations, providing a stable and adjustable work surface.
     

• Safety: When handling and modifying steel tracks, ensure proper safety measures are in place. Wear appropriate protective gear, such as gloves and eye protection, to prevent injuries.
  
• Tools and Equipment: Depending on the intended repurposing project, you may need specialized tools like welding machines, grinders, or cutting equipment. Ensure you have access to the necessary tools and are trained in their use.
  
• Legal and Environmental Compliance: Before repurposing steel tracks, check local regulations regarding the reuse of industrial materials. Additionally, consider the environmental impact and ensure that any modifications or disposals are conducted responsibly.
  

The 262C and Its Role in Compact Equipment Evolution
The Caterpillar 262C skid steer loader was introduced in the late 2000s as part of CAT’s C-series, designed to deliver high performance in compact form. With a rated operating capacity of 2,700 pounds and a vertical lift path, the 262C was built for material handling, grading, and attachment versatility. Caterpillar, founded in 1925, had by then become a global leader in construction machinery, and the C-series reflected its push toward operator comfort, hydraulic refinement, and electronic integration.
The 262C features a turbocharged CAT C3.4T diesel engine rated at 82 horsepower, a high-flow hydraulic option, and joystick pilot controls. Its sealed and pressurized cab, optional air conditioning, and advanced monitoring system made it a favorite among contractors and rental fleets.
Terminology annotation:
- Vertical lift path: A loader arm design that maintains a straight upward trajectory, ideal for lifting and loading into trucks.
- High-flow hydraulics: An enhanced auxiliary hydraulic system capable of powering demanding attachments such as cold planers and mulchers.
- Pilot controls: Hydraulic-actuated joysticks that offer smoother and more responsive operation than mechanical linkages.
Key Specifications and Features
Standard configuration includes:

• Engine: CAT C3.4T, 82 hp
  
• Operating weight: ~8,000 lbs
  
• Rated operating capacity: 2,700 lbs
  
• Hydraulic flow: Standard 22 GPM, High-flow 33 GPM
  
• Travel speed: Up to 12 mph with two-speed transmission
  
• Cab: Sealed and pressurized with optional HVAC
  
• Attachments: Compatible with buckets, forks, augers, trenchers, sweepers, and more
  

• Excellent condition, low hours (<2,000): $32,000–$38,000
  
• Mid-range condition, moderate hours (2,000–3,500): $25,000–$30,000
  
• High hours (>4,000), open cab, basic hydraulics: $18,000–$24,000
  
• Rental fleet units with documented service history: $28,000–$34,000
  

• Enclosed cab with HVAC
  
• Two-speed transmission
  
• High-flow hydraulics
  
• Recent undercarriage or tire replacement
  
• Included attachments (e.g., bucket, forks, grapple)
  

• Hydraulic leaks or worn hoses
  
• Engine blow-by or injector imbalance
  
• Faulty joystick controls or electrical issues
  
• Cosmetic damage or rust
  

• Check hydraulic pressure and flow at couplers
  
• Inspect engine for blow-by and oil leaks
  
• Test joystick responsiveness and monitor panel
  
• Verify cab seals and HVAC function
  
• Review service records and fluid change intervals
  
• Measure tire tread depth and look for uneven wear
  
• Operate attachments to confirm compatibility and flow
  

• Budget $2,000–$4,000 for post-purchase repairs and upgrades
  
• Prioritize units with documented maintenance history
  
• Avoid machines with electrical faults unless discounted heavily
  
• Use CAT ET software for diagnostic checks if available