Merlo 268 – UCMS / UGSG / ROTO MCSS / MERLIN: Stage Rotation Speed Faulty

The control system has detected an anomaly in the rotational speed of the machine's turret (stage), indicating that it is not operating within the expected parameters. The system expects the turret to rotate within specific parameters, and this code is triggered when the measured speed is incorrect or absent. The underlying cause is cited as a sensor or engine fault, but can also be related to CAN bus communication errors or mechanical/hydraulic issues with the rotary actuator.

• R40.25
• R40.26
• R45.21

1. 1

   Visually inspect the wiring harness leading to the turret rotation sensor for any signs of damage, such as chafing, crushing, or corrosion.

2. 2

   Ensure all electrical connectors for the turret rotation sensor and the UCMS controller are secure and free of contamination.

3. 3

   Check for any other CAN bus-related fault codes (typically in the 2xx range) that might indicate a broader communication error.

4. 4

   Connect a Merlo diagnostic tool (MerloDiag or MerloTOOL) to read live data from the rotation sensor and check for related errors.

1. 1

   Prepare machine for service

   Park the machine on level ground, lower the boom, and engage the parking brake. Turn off the engine and disconnect the battery before working on electrical components.

2. 2

   Locate rotation sensor

   Identify the turret rotation speed/position sensor. It is typically an angle or position encoder located on or near the rotary actuator/gearbox that drives the turret's rotation.

3. 3

   Test sensor output

   Test the sensor's output signal according to the specifications in the machine's service manual. Check for a specific voltage or pulse signal as the turret is manually rotated (if safe to do so). Look for an open circuit or a short circuit.

4. 4

   Inspect rotary actuator

   If the sensor tests normal, inspect the mechanical and hydraulic components responsible for turret rotation for any signs of binding, damage, or hydraulic issues that could cause an erratic speed.

5. 5

   Replace faulty sensor

   If the sensor is determined to be faulty during testing, replace it with a new unit.

6. 6

   Calibrate system

   After replacing the sensor or performing other repairs, use the Merlo diagnostic tool to calibrate the system. This ensures the control system recognizes the new component and its position correctly.

7. 7

   Final system check

   Clear the fault codes and operate the machine to ensure the 'Stage Rotation Speed Faulty' error does not reappear.