Common Causes, Diagnostics, and What To Do About It

Few things are more frustrating than powering up a robot… and watching it sit there like it’s on strike. No movement, no sound, maybe even no response at all.

The Good News; Most “stuck” DYNAMIXEL issues are not permanent failures. They’re usually caused by configuration, protection features doing their job, or recoverable firmware states.

The Bad News; This can also mean more serious problems, such as internal damage, faulty connections, or even dead components.

This post walks through all the common reasons a DYNAMIXEL actuator might not move, how to diagnose each one, and what to do, from quick fixes, to firmware resets and RMA.

1. Torque Is Disabled (The #1 Cause)

This is the most common issue by far, and almost everyone runs into it at least once. DYNAMIXEL actuators will not move unless torque is explicitly enabled. Even if your software is sending position or velocity commands, the actuator will remain motionless if torque is turned off.

You can verify this by checking the Torque Enable item in the control table. The value must be set to 1. If it’s 0, the actuator is effectively in a passive state. 

What to do:

Enable torque through your control software, such as:

2. The Actuator Is in the Wrong Operating Mode

Many DYNAMIXEL actuators support multiple operating modes, including position, extended position, velocity, current, current-based position and PWM control. If your controller is sending position commands while the actuator is configured for velocity mode, nothing will happen - even though communication appears normal.

Before enabling torque, always confirm that the operating mode matches the type of commands you’re sending. This mismatch is easy to overlook, especially when reusing code or swapping actuators, but it’s also one of the simplest problems to fix once you spot it.

3. Built-In Safety Protections Have Kicked In

DYNAMIXEL actuators continuously monitor their own health. If something goes wrong, they may automatically disable torque.

Common triggers include:

When this happens, the actuator may appear “dead,” even though it’s actually behaving correctly. Checking the Hardware Error Status register will usually reveal what caused the shutdown. Power-cycling the actuator, reducing mechanical load, and correcting the underlying issue will often allow you to safely re-enable torque and resume operation.

4. Mechanical Resistance or Overload

Not all problems are electrical or software-related. Mechanical issues can completely prevent motion, even when everything else looks fine. An actuator that is overloaded, misaligned, or physically blocked may refuse to move or immediately disable torque.

A good test is to disable torque and gently rotate the output shaft by hand. If the actuator moves freely when removed from the robot but not when installed, the issue is likely external - such as binding, excessive load, or poor alignment in the mechanism.

If the actuator cannot move on its own with no load attached, the actuator will likely need to be repaired or replaced. Luckily, repairing the actuator through the RMA process often costs much less than purchasing a new actuator.

5. Position Limits Are Blocking Movement

DYNAMIXEL actuators respect configured motion limits.

If the commanded position falls outside the allowed range, the actuator will simply refuse to move.

What to check:

Make sure your goal position is safely within these bounds.

6. Communication Looks Fine… But Isn’t

Sometimes the actuator isn’t stuck, it just isn’t hearing you. Communication problems can be subtle and misleading, especially if other devices on the bus appear to work.

Common causes include incorrect baud rates, mismatched protocol versions, duplicate IDs, or loose or damaged cables. Running a device scan in DYNAMIXEL Wizard is often the fastest way to confirm whether the actuator is actually responding and whether its settings match your controller’s expectations.

7. Power Supply Issues

DYNAMIXEL actuators require stable voltage and sufficient current, particularly under load. An underpowered system may allow communication but fail the moment motion is attempted.

Symptoms of power problems include actuators resetting during movement, flickering LEDs, or motion that only works when no load is applied. Make sure your power supply meets the actuator’s specifications, and avoid powering motors directly from USB ports or logic rails.

When a Reset Makes Sense

If the actuator communicates but behaves unpredictably, a reset can help.

Factory Reset

Restores default configuration (ID, baud rate, limits, mode).

Great for:

Firmware Recovery

If things are really off:

How to Quickly Validate a DYNAMIXEL Actuator

Before assuming failure:

When It’s Time for RMA

In some cases, hardware failure is unavoidable. All mechanical systems experience wear over time, and robotics components are no exception.

Consider RMA if the actuator:

Having clear test results and setup details will speed up the process.

Remember - 

A non-moving DYNAMIXEL actuator is usually not broken, it’s waiting for the right conditions.

Start with:

Torque > Operating mode > Errors > Mechanics > Adequate Power

Once those are confirmed, you’re often just one small control table change away from motion.