Troubleshooting blown fuse during engine start
Table of Contents:
- Introduction
- Customer Complaint and Initial Diagnosis
- Understanding the Schematic Diagram
- Analysis of the Key Switch Fuse
- Identifying the Power Feed Issue
- Locating the Wiring Problem
- Fixing the Issue
- Testing the Solution
- Preventive Measures
- Conclusion
Introduction
In this article, we will discuss a specific issue with a Lugong diesel vehicle that was brought in by a customer. The complaint was related to a blown fuse during the starting process. We will go through the steps taken to diagnose and resolve the problem, providing a detailed analysis of the wiring issue and the necessary repairs. By understanding this case study, you'll gain insights into troubleshooting electrical problems in similar vehicles.
Customer Complaint and Initial Diagnosis
The customer's complaint was that the Lugong vehicle's fuse would always blow when attempting to start the engine. To investigate the issue, an initial diagnosis was made, and an adapter was used to connect regular fuses for testing purposes.
Understanding the Schematic Diagram
To understand the root cause of the blown fuse, it was essential to analyze the schematic diagram of the truck's electrical system. This diagram helped identify the key switch fuse, which supplies power to the key switch.
Analysis of the Key Switch Fuse
Upon further investigation, it was discovered that the key switch fuse, a 15-amp fuse, was responsible for supplying power to the key switch. Surprisingly, the fuse did not blow when the key was turned on but did blow during the cranking process. This finding pointed toward a problem in the starting circuit.
Identifying the Power Feed Issue
Detailed examination of the schematic diagram revealed that the key switch fuse sent power to the MCU (Microcontroller Unit). From there, the MCU supplied power to the starter relay through a specific path. The focus now shifted to identifying the power feed issue within this path.
Locating the Wiring Problem
Using a test light, the positive end of the circuit was connected, and the location of the starter relay was examined. It was observed that there was a burn mark and the absence of a power feed where it should have been present. Careful inspection revealed a wire in the harness that had been damaged due to contact with a mounting bracket.
Fixing the Issue
The next step involved removing the zip tie that held the harness in place and inspecting the damaged wire more closely. It was evident that the mounting bracket had been rubbing against the wire, gradually causing damage over time. The wire was no longer in contact with the bracket, and the relay could be reinstalled.
Testing the Solution
Before finalizing the repair, a test was conducted to ensure the issue had been resolved. By connecting the test light to the positive end, it was confirmed that there was no longer a negative on the wire tip. With this positive outcome, the relay was reinstalled.
Preventive Measures
To prevent similar issues in the future, it was suggested to relocate the wire or use protective wrap to prevent contact with any brackets. This would help avoid any accidental damage to the wire harness during vehicle operation.
Conclusion
In conclusion, the blown fuse issue in the Lugong diesel vehicle was successfully diagnosed and resolved by identifying a wiring problem caused by contact with a mounting bracket. By following the steps outlined in this article, other automotive professionals can gain insights into troubleshooting similar electrical issues.
Highlights:
- Customer complaint of blown fuse during starting process.
- Diagnosis reveals a wiring issue.
- Analysis of the schematic diagram helps identify the key switch fuse.
- Wiring problem found due to contact with a mounting bracket.
- Wire relocated and preventive measures suggested for future incidents.
FAQ Q&A:
Q: What was the customer's complaint with the Lugong vehicle?
A: The customer complained that the fuse would blow when starting the engine.
Q: What was the cause of the blown fuse?
A: The blown fuse was caused by a wiring problem due to contact with a mounting bracket.
Q: How was the issue resolved?
A: The damaged wire was relocated and measures were suggested to prevent future incidents.
Q: What did the analysis of the schematic diagram reveal?
A: The analysis helped identify the key switch fuse and the power feed path.
Q: What precautionary steps were suggested?
A: It was suggested to relocate the wire or use protective wrap to prevent future damage.
