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Overview of the Daewoo DH50
The Daewoo DH50 is a compact hydraulic excavator introduced in the mid-1990s, designed for urban construction, trenching, and utility work. Daewoo Heavy Industries, a South Korean manufacturer, was known for producing durable and cost-effective machines before merging into Doosan Infracore in the early 2000s. The DH50 features a conventional tail swing, a diesel engine rated around 50 hp, and a straightforward electrical system that relies on mechanical relays and fusible links rather than complex ECUs. Thousands of DH50 units were sold across Asia and Europe, and many remain in service today due to their mechanical simplicity.
Symptoms of the Starting Problem
A common issue with aging DH50 units is failure to crank when the key is turned to the start position. In one case, the ignition switch activated the heater plugs and auxiliary circuits correctly, and a large relay near the front of the machine clicked when the key was turned—but the starter solenoid did not engage. Jumping the solenoid manually caused the engine to crank, confirming that the starter motor itself was functional.
This behavior suggests a break in the control circuit between the ignition switch and the starter solenoid. The solenoid wires—yellow and white, approximately 2.5 mm in diameter—were not connected directly to the ignition switch, indicating the presence of an intermediate device.
Identifying the Circuit Breaker and Fusible Link
Further investigation revealed that the fault lay in a circuit breaker, also referred to as a fusible link, which was creating a significant voltage drop when the key was turned to the start position. This prevented sufficient current from reaching the solenoid. Shorting the circuit breaker temporarily restored function, confirming it as the source of the problem.
Fusible links are designed to protect the electrical system from overloads, but over time they can degrade internally, especially in machines exposed to moisture or vibration. In the DH50, the fusible link is located near the battery or starter relay cluster and may be enclosed in a plastic housing.
Wiring Diagram and Diagnostic Strategy
A wiring diagram for the DH50 was obtained from a third-party manual distributor, allowing technicians to trace the starter circuit. The diagram showed that the starter solenoid is fed through the ignition switch, a relay, and the fusible link. Interestingly, the diagram also referenced an engine stop relay and motor connected to the ACC terminal of the ignition switch, though this component was not present on the specific DH50 unit in question.
To diagnose similar issues:
Field Experience and Practical Advice
In 2014, a technician in Melbourne encountered a similar issue on a Daewoo 300LCV, where the machine would not start or stop using the key. Power was present at key terminals, but the start signal failed to reach the solenoid. The solution involved tracing the wiring harness and replacing a degraded fusible link near the firewall.
Operators working with older Daewoo machines should:
Starting problems on the Daewoo DH50 are often caused by degraded fusible links or corroded relay connections. With basic electrical tools and a wiring diagram, these faults can be diagnosed and resolved without major component replacement. The DH50’s mechanical simplicity makes it a forgiving platform for field repairs, and with proper maintenance, it can continue serving reliably for years to come.
The Daewoo DH50 is a compact hydraulic excavator introduced in the mid-1990s, designed for urban construction, trenching, and utility work. Daewoo Heavy Industries, a South Korean manufacturer, was known for producing durable and cost-effective machines before merging into Doosan Infracore in the early 2000s. The DH50 features a conventional tail swing, a diesel engine rated around 50 hp, and a straightforward electrical system that relies on mechanical relays and fusible links rather than complex ECUs. Thousands of DH50 units were sold across Asia and Europe, and many remain in service today due to their mechanical simplicity.
Symptoms of the Starting Problem
A common issue with aging DH50 units is failure to crank when the key is turned to the start position. In one case, the ignition switch activated the heater plugs and auxiliary circuits correctly, and a large relay near the front of the machine clicked when the key was turned—but the starter solenoid did not engage. Jumping the solenoid manually caused the engine to crank, confirming that the starter motor itself was functional.
This behavior suggests a break in the control circuit between the ignition switch and the starter solenoid. The solenoid wires—yellow and white, approximately 2.5 mm in diameter—were not connected directly to the ignition switch, indicating the presence of an intermediate device.
Identifying the Circuit Breaker and Fusible Link
Further investigation revealed that the fault lay in a circuit breaker, also referred to as a fusible link, which was creating a significant voltage drop when the key was turned to the start position. This prevented sufficient current from reaching the solenoid. Shorting the circuit breaker temporarily restored function, confirming it as the source of the problem.
Fusible links are designed to protect the electrical system from overloads, but over time they can degrade internally, especially in machines exposed to moisture or vibration. In the DH50, the fusible link is located near the battery or starter relay cluster and may be enclosed in a plastic housing.
Wiring Diagram and Diagnostic Strategy
A wiring diagram for the DH50 was obtained from a third-party manual distributor, allowing technicians to trace the starter circuit. The diagram showed that the starter solenoid is fed through the ignition switch, a relay, and the fusible link. Interestingly, the diagram also referenced an engine stop relay and motor connected to the ACC terminal of the ignition switch, though this component was not present on the specific DH50 unit in question.
To diagnose similar issues:
- Test voltage at the solenoid terminal when the key is turned to start
- Check continuity across the fusible link using a multimeter
- Inspect relay terminals for corrosion or loose connections
- Verify ignition switch output at each key position
Field Experience and Practical Advice
In 2014, a technician in Melbourne encountered a similar issue on a Daewoo 300LCV, where the machine would not start or stop using the key. Power was present at key terminals, but the start signal failed to reach the solenoid. The solution involved tracing the wiring harness and replacing a degraded fusible link near the firewall.
Operators working with older Daewoo machines should:
- Keep a printed wiring diagram on hand
- Label wires during troubleshooting
- Use dielectric grease on connectors to prevent corrosion
- Replace aging relays and links proactively
Starting problems on the Daewoo DH50 are often caused by degraded fusible links or corroded relay connections. With basic electrical tools and a wiring diagram, these faults can be diagnosed and resolved without major component replacement. The DH50’s mechanical simplicity makes it a forgiving platform for field repairs, and with proper maintenance, it can continue serving reliably for years to come.
