The motor does not turn at all, how do I check it step by step?
Work from the source towards the load: battery voltage, fuse, voltage at the driver supply terminals, input command signal, driver output voltage and finally the motor. Measuring under load is critical; if a system showing 12.6 V unloaded drops to 9 V when load is applied, the problem is in the wiring or the battery.
Ordered checklist:
- Battery / source voltage: Measure both unloaded and at the moment the command is given. If there is a serious drop under load, the battery is weak or the cable cross-section is insufficient.
- Fuse: Visual inspection is misleading; measure continuity across both ends.
- Driver supply terminals: Measure the voltage at the terminal block, not at the battery post. The difference between the two shows all the line losses. If the reading is low here, look for the fault along the line.
- Chassis return: Measure the voltage between the driver chassis terminal and the battery negative post under load; more than a few hundred millivolts points to a bad return connection.
- Input command: When the button is pressed or the remote control is used, does a signal appear at the relevant input terminal (IN1–IN4 on the KS250, A–D on the PT500)? If you are working over RF, also verify that the receiver is powered and producing an output.
- Driver output: Measure the voltage at the motor terminals while the command is applied. If voltage is present and the motor does not turn, the problem is in the motor or the mechanics.
- Motor: Apply supply directly to its terminals briefly. If it does not turn, the motor or the mechanics are seized.
Additional checks: reverse polarity connection, a loose terminal, the current limit pot set close to zero, and the movement already resting against its end stop are common simple causes.
Full topic: DC Motor Driver Selection Guide