Today we are going to discuss the Mitsubishi MR-S11/S12 Servo Drives as well as their typical failures. Below we list common alarm codes associated with these servo drives from Mitsubishi and a few troubleshooting steps you can take.

Remember, it is very important that you maintain proper safety while troubleshooting your CNC Equipment. If you missed our blog on proper troubleshooting safety, check it out HERE to learn the dos and don’ts.

Overview of Series:

Mitsubishi MR-S11/S12 AC servo drives are a direct replacement for the older MR-S1 and MR-S2 units, respectively. A few of the features that this series offers are an enhanced all-digital control which was used previously in the conventional MR-S series systems, individual CPUs used to control individual axes, allowing enhanced machining accuracy, and gate array control card components which allow improved reliability by using fewer cables and parts.

Benefitting from a pair of built-in seven-segment screens, the users can easily read alarm codes in cases of machine malfunction. The full list of alarms can be found {HERE}, but one of the most common (alarm 32) will be briefly coved below.

Common Failures – Alarm Codes and Troubleshooting Steps:

Alarm 32 indicates a detected overcurrent. This can be triggered by issues within the motor, the motor cabling, or component failure within the drive unit itself. Occasionally, a failure stemming from the motor can lead to the drive components failure, therefore both of the following tests are highly recommended, even if something is found during the first test.

For overcurrent issues, there are a few quick checks which can be done while on-site to help isolate where the failure is being produced from.

Weak insulation within the motor or the motor cables

This is one of the most common causes of overcurrent alarms that we see. To check this on site, an insulation tester, or also known as a megger, would be required. Here’s a quick video on how to check the motor using a megger:

Please visit our store to purchase this tool online. Alternatively, contact our sales department at (847)-465-9060 and we will be happy to assist you with this purchase. A standard multimeter can be used following the megger test to check resistance between each combination of legs from the motor (U-V, V-W, U-W), all of which should come up with relatively low readings, and each reading should be of the same value.

Issues with the MR-S output section

As we mentioned earlier, sometimes the issues that originated within the motor lead to the drive components failure. One of the first things that can be done to verify the drive integrity is to confirm that the motor leads (U, V and W) are disconnected and attempt to power up the machine again. Try to reproduce the issue the way it occurred originally. If the overcurrent alarm persists, the output of the drive itself has been damaged and requires further evaluation and possibly repair.

For any additional technical support, troubleshooting, or inquiries regarding repair or to purchase MR-S11/S12 drive units, please contact us at (847)-465-9060 and one of our customer service representatives would be happy to assist you. 

At Precision Zone, we guide our clients toward the best decisions that serve their business needs. If you have specific repair or replacement questions, get in touch with our expert customer support team at 800-551-4420 or

Written by:

Marketing & Creative Director at IcarTeam, and supporting afiliated businesses,
including Precision Zone, Precision Education Integrators and Alfra Tools.
Did you like this article? Click your favorite social media channel to share it with your friends and colleagues
You might also enjoy these articles:
Recent articles:


You know who we are, what we do and how we do it, so let's get started!


Get the latest news, tips, insights and product spotlights sent straight to your inbox weekly

By entering your email, you agree to our Terms of Service and Privacy Policy.
Call Us Now!