What is Kato HD820-1 Fault Code E35?

Fault Code E35 on the Kato HD820-1 excavator indicates a malfunction in the swing motor overheat protection circuit or temperature sensor system. This diagnostic trouble code (DTC) is triggered when the Electronic Control Module (ECM) detects abnormal temperature readings from the swing motor thermal sensor or identifies a circuit failure in the monitoring system.

The swing motor is critical for the HD820-1's upper structure rotation, and excessive heat can lead to hydraulic oil degradation, seal failure, and catastrophic motor damage. The temperature monitoring system protects this expensive component by alerting operators before thermal damage occurs. In used excavators, this code often appears due to sensor degradation, wiring corrosion, or actual overheating from worn mechanical components that increase friction and heat generation.

Common Symptoms

When Code E35 is active on your Kato HD820-1, operators typically experience:

• Swing function limitation or complete shutdown – the ECM may derate or disable swing operations to prevent motor damage
• Intermittent warning lamp illumination on the instrument cluster, often accompanied by an audible alarm
• Reduced swing speed even before complete shutdown, as the system enters protective mode
• Abnormally hot swing motor housing upon physical inspection (though the code may trigger before this is noticeable)
• Code storage in ECM memory even after the machine cools down, requiring manual reset

Potential Causes

The most common technical causes for E35 in used HD820-1 excavators include:

• Faulty swing motor temperature sensor – thermistors degrade over time, providing false high-temperature readings to the ECM
• Damaged or corroded wiring harness between the sensor and ECM, particularly at connection points near the swing bearing where vibration and exposure occur
• Actual swing motor overheating due to contaminated hydraulic oil, worn bearings, or insufficient lubrication in aging machines
• Poor electrical ground connections at the sensor mounting point, causing erratic signal voltage
• ECM calibration drift or software corruption in older control modules
• Hydraulic system issues causing excessive back-pressure and heat generation (worn swing motor seals or restricted lines)

How to Troubleshoot and Fix Code E35

Step 1: Visual Inspection and Initial Checks Begin by allowing the machine to cool completely. Inspect the swing motor temperature sensor (typically located on the motor housing) for physical damage, loose connections, or corrosion. Check the wiring harness from the sensor to the main harness for abrasion, especially where it passes near the swing bearing race—a common wear point on used excavators.

Step 2: Electrical Testing Using a digital multimeter, measure the sensor resistance. The thermistor should typically read between 2-10 kΩ at ambient temperature (consult the Kato service manual for exact specifications). Check for continuity in the wiring harness and verify proper ground connection (should read less than 1 Ω to chassis ground). If available, use Kato diagnostic software to monitor live temperature data and compare it to actual motor temperature measured with an infrared thermometer.

Step 3: Component Replacement and System Verification If the sensor reads open circuit, short circuit, or out-of-range values, replace the temperature sensor with a genuine Kato part. Before installation on used equipment, clean all electrical connectors with contact cleaner and apply dielectric grease to prevent future corrosion. If electrical components test correctly, investigate actual overheating causes: check hydraulic oil condition, inspect swing motor bearings and seals, and verify proper oil cooler function.

Step 4: Clear Codes and Test Operation After repairs, clear the fault code using diagnostic software or by disconnecting the battery negative terminal for 5 minutes. Operate the swing function under normal load while monitoring temperatures. On used machines, perform this test gradually to ensure repairs are effective before returning to full production.

---

Disclaimer: This guide provides general troubleshooting information for Code E35 on Kato HD820-1 excavators. Always consult the manufacturer's official service manual and consider professional diagnostic assistance for complex electrical or hydraulic issues, especially on used equipment where multiple systems may be degraded.