Tool changer is not rotating when pressing the tool change key on the CNC controller.

Measure the voltage between the TL+(tool changer forward signal) and +24V, the result is 4V which is obviously abnormal. It should be +24 for changing the tool and 0V for not.

And the IC2803 of CNC controller is fine.

According to the operator that there was a DC relay burned, after change it the problem occurred, this might be the problem.

Then we found the dock of the DC relay was break-down, change it the problem solved.