Hyundai R805LC-7 Fault Code 135: Complete Diagnostic Guide

What is Hyundai R805LC-7 Fault Code 135?

Fault Code 135 on the Hyundai R805LC-7 excavator indicates a malfunction in the Swing Motor 1 Solenoid Valve circuit, specifically detecting an abnormal electrical signal or open/short circuit condition.

This fault code is generated when the Electronic Control Module (ECM) detects voltage irregularities in the swing motor's proportional solenoid valve circuit. The swing system is critical for the R805LC-7's operational efficiency, as it controls the upper structure's rotational movement. When this circuit fails, the ECM cannot properly regulate hydraulic oil flow to the swing motor, directly impacting machine productivity and potentially causing uneven or restricted swing operation. This is particularly concerning in used excavators where electrical connectors and wiring harnesses may have accumulated thousands of operating hours in harsh conditions.

Common Symptoms

When Fault Code 135 is active on your R805LC-7, operators typically experience:

• Illuminated malfunction warning light on the main instrument panel with reduced swing performance
• Erratic or sluggish swing movement, often inconsistent in one or both directions
• Complete loss of swing function while other hydraulic operations remain normal
• Audible warning alarm accompanied by error message on the digital display
• Swing speed limitation or failure to achieve normal swing RPM under load

Potential Causes

The most common technical failures triggering Code 135 in used R805LC-7 excavators include:

• Damaged solenoid valve wiring harness due to chafing against the swing bearing race (known wear point on this model)
• Failed proportional solenoid coil in the main control valve assembly
• Corroded or loose electrical connectors at the swing motor solenoid valve
• Short circuit to ground caused by pinched wires in the center joint routing area
• Open circuit from broken internal wiring within the harness flex section
• ECM internal fault (rare, but possible in high-hour machines)

How to Troubleshoot and Fix Code 135

Step 1: Visual Inspection Begin by inspecting the swing motor solenoid valve connector located on the main control valve. Check for corrosion, moisture intrusion, or damaged pins. On used excavators, carefully trace the wiring harness through the center joint—this is a critical wear point where cables flex during swing operation.

Step 2: Electrical Testing Using a digital multimeter, disconnect the solenoid connector and measure coil resistance. Typical specification is 3-7 ohms (consult service manual for exact values). Next, check for voltage supply from the ECM with ignition on—should read approximately 12-24V depending on circuit design. Test for short to ground by measuring resistance between each wire and chassis ground (should read infinite resistance).

Step 3: Harness and Connector Repair If resistance values are abnormal, inspect for wire breaks inside the insulation. In used machines, carefully examine connector pins for heat damage or backing-out. Clean all connections with electrical contact cleaner and apply dielectric grease before reassembly.

Step 4: Component Replacement If the solenoid coil tests faulty (incorrect resistance or physical damage), replace the proportional solenoid valve cartridge. Use genuine Hyundai parts to ensure proper PWM signal compatibility with the ECM. After replacement, clear codes using Hi-MATE diagnostic software or equivalent and perform operational tests.

---

Disclaimer: This guide provides general diagnostic information. Always consult the official Hyundai R805LC-7 service manual and consider professional assistance for complex electrical repairs. Improper diagnostics may cause additional system damage.