Merlo P40.17 Boom Fails to Extend Past First Stage
Fault Codes & Symptoms
Boom extension stops at first stage Related symptoms: - Inaccurate boom length reading on the operator display. - Erratic load chart information or premature lockout by the LMS. The operator reports that the boom will telescope out to a certain point and then stops, preventing full reach.
Confirmed cause: Internal failure of the boom extension position sensor. The sensor had a dead spot that corresponded with the end of the first stage of extension. Repair performed: The faulty boom extension sensor was replaced with a new part. The sensor cable and its routing were inspected for potential damage, and none was found. Verification: After sensor replacement, the system was re-calibrated according to the manufacturer's procedure. The boom was then cycled multiple times, confirming that it could extend smoothly through all stages to its full length without stopping prematurely. Technician notes: - The fault did not generate a specific error code, making hands-on electrical testing essential. - The failure was position-dependent, not time-dependent. Always check sensor signals through their full range of motion. - Be sure to follow the official calibration procedure after replacing any position sensor related to the load management system to ensure safe operation.