The Mitsubishi HC153S-SZ / HC153S-A42 motor was sent to us by an automotive supplier. The customer wanted to test our capabilities and evaluate if we could become a reliable long-term partner for motor repairs. The pressure was high, since downtime in the automotive industry means immediate production line stoppage.

Symptoms: Encoder errors and sporadic short circuits

At first, the motor only showed sporadic encoder errors, causing occasional machine disturbances. But the situation escalated quickly. The motor no longer started reliably and eventually caused short circuits, resulting in a complete machine shutdown. For the customer, it was clear: a fast and competent repair was required.

Root cause: Water ingress through defective shaft seal

Upon disassembly the cause became evident: moisture had entered the housing through an aged shaft seal. Coolant had spread inside, leaving corrosion on stator laminations, connectors, and housing surfaces. The OSA104S2 encoder was severely affected, producing unstable signals that brought the entire drive system to a halt.

Repair process: Step by step back to reliability

To restore the motor, we carried out a complete disassembly:

• Bearing replacement: Defective ball bearings were replaced with new precision bearings to ensure smooth operation.
• Seal renewal: New shaft seals were installed to prevent further coolant ingress.
• Thorough cleaning and oven drying: All components were cleaned and then dried for several hours in an industrial oven to remove residual moisture.
• Connector overhaul: Corroded contacts were cleaned, treated, and preserved with protective grease.
• Encoder replacement: The defective OSA104S2 was replaced by a refurbished spare unit from our stock, carefully adjusted and reprogrammed.

Final testing: Load test on our Mitsubishi test bench

After reassembly the motor had to prove its reliability. Testing was carried out on our Mitsubishi MDS-C1-V1-20 test bench:

• Insulation measurement: Ensuring electrical safety.
• No-load test: Checking smooth and vibration-free rotation.
• Load test: Simulating real machine conditions with torque load.
• Signal monitoring: Continuous observation of encoder signals for stability and accuracy.

All tests were successful. The motor achieved full performance again and was returned to the customer.

Results: Building trust through competence

The successful project convinced the customer. The motor was back in operation and the production line could continue without restrictions. For us, this repair was a door opener: the customer realized that even critical cases could be solved professionally with our expertise.

Prevention: Avoid failures before they occur

We recommended the customer to perform regular inspections of shaft seals and to check connectors for signs of moisture ingress. A scheduled preventive overhaul after several thousand operating hours can also help prevent costly downtime. This significantly extends the motor’s lifetime and secures reliable production.

To mentioned Mitsubishi Motor: Mitsubishi Servo Motor HC153S-SZ / HC153S-A42 mit Encoder OSA104S2

More details about our Mitsubishi repair services can be found here:
Mitsubishi motor Repair by Industrypart

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Technical Specifications

Application & compatible devices

This motor is widely used in machine tools, automation lines, and handling systems.
Compatible drives are Mitsubishi MDS-B, MDS-C1, MR-J2S and certain MR-J3 controllers.
Applications: CNC machining centers, robotic axes, spindle and feed drives.

Functional description

The HC153S-SZ / HC153S-A42 is a high-precision AC servo motor equipped with the OSA104S2 absolute encoder. It enables exact positioning and reliable feedback for dynamic axes.
Its robust design with shaft seal makes it suitable for harsh industrial environments, provided seals are regularly inspected.

Alarms & Troubleshooting

Components