08-21-2025, 06:23 PM
Machine Overview
The Bomag BW120 AD-3 is a compact, versatile vibratory double drum roller widely used in asphalt compaction and soil stabilization. It features a 33 hp Deutz diesel engine, hydrostatic travel and vibration drive systems, and weighs approximately 6,000 lbs (around 3 tons), making it well-suited for medium to small road and landscaping projects.
Key specifications include:
Users have reported issues with the brakes not releasing properly on the Bomag 120 AD-3. Specifically, the brakes remain engaged, preventing machine movement even when the system should allow release. Testing shows:
The Bomag BW120 AD-3 is a reliable compact vibratory roller favored for asphalt and soil compaction in urban and small-scale projects. However, brake engagement issues have been reported, frequently linked to electrical faults involving the brake solenoid and its controlling relays. Diagnosing the problem requires testing relays, wiring, and control circuits with reference to the machine’s electrical schematics. Preventive maintenance focusing on electrical system cleanliness and integrity, along with adherence to service schedules, can help minimize downtime caused by such brake issues.
The Bomag BW120 AD-3 is a compact, versatile vibratory double drum roller widely used in asphalt compaction and soil stabilization. It features a 33 hp Deutz diesel engine, hydrostatic travel and vibration drive systems, and weighs approximately 6,000 lbs (around 3 tons), making it well-suited for medium to small road and landscaping projects.
Key specifications include:
- Vibratory double drum with variable frequency and amplitude.
- Hydrostatic drive providing smooth speed control and efficient power transmission.
- Compact design with operator-friendly controls for enhanced productivity and comfort.
- Equipped with scrapers on both drums to prevent material buildup.
- A pressure sprinkler system ensures even wetting of drum surfaces for optimal compaction performance.
Users have reported issues with the brakes not releasing properly on the Bomag 120 AD-3. Specifically, the brakes remain engaged, preventing machine movement even when the system should allow release. Testing shows:
- E-stop switch, ignition, forward/reverse control, and seat switches function correctly.
- Directly powering the brake solenoid releases the brakes and restores normal operation.
- The difficulty lies in locating and testing the related relays that control the brake solenoid, leading to significant troubleshooting time without success.
- The problem is likely electrical, involving the relay(s) or wiring controlling the brake solenoid.
- Relay contacts may be faulty, or the relay may not be receiving control signals properly.
- Wiring harness issues, such as loose connectors, corrosion, or broken wires, can interrupt signal flow.
- Control switches, although tested, should be inspected in situ during operation for intermittent faults.
- Consulting the machine's wiring diagram and relay locations in the service manual helps narrow down the fault.
- Measuring voltage to the solenoid relay coil and contacts during different operational states is essential.
- Cleaning or replacing suspected relays and connectors often resolves brake engagement problems.
- Regular inspection and cleaning of electrical connections reduce relay and solenoid failures.
- Keep the brake system components free of debris and properly lubricated as per the maintenance schedule.
- Review recent work or events preceding the problem—excessive moisture, vibration, or impacts might contribute to issues.
- Solenoid: An electromechanical device converting electrical energy into mechanical movement to engage or release brakes.
- Relay: An electrically operated switch that controls a circuit by a separate low-power signal.
- Hydrostatic Drive: A transmission system using hydraulic fluid to transfer power, allowing smooth and variable speed control.
- Pressure Sprinkler System: Mechanism that sprays water on the drums to prevent sticking of asphalt during compaction.
The Bomag BW120 AD-3 is a reliable compact vibratory roller favored for asphalt and soil compaction in urban and small-scale projects. However, brake engagement issues have been reported, frequently linked to electrical faults involving the brake solenoid and its controlling relays. Diagnosing the problem requires testing relays, wiring, and control circuits with reference to the machine’s electrical schematics. Preventive maintenance focusing on electrical system cleanliness and integrity, along with adherence to service schedules, can help minimize downtime caused by such brake issues.
