As far as the motors are concerned, we need to check three things. Firstly, we need to check whether all four motors spin. If you check this via the software you are using, there would always be a tab for the motors. Usually, you can spin your motors through Cleanflight, Mission Planner, or any other software. Another simple way of doing this is to unplug your ESC servo wire and connect it to your receiver throttle pin. Since everything will power up as normal, you can increase your throttle and, hopefully, spin the motor that is connected to your ESC.

The second thing that we should check is whether the brushless motor spins clockwise or counterclockwise. We can change it by simply changing the connection between the motor and the ESC. There should be three wires, as shown in the following image:

If we disconnect two of the wires and connect them to a hitch, the motor will turn in the opposite direction. Remember that the motor order in the APM flight controller is as follows...