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One of Four T200 Motors Not Spinning

I’m working on constructing an ROV for a science project. We are using four T200 motors as thrusters for the ROV. The ROV is currently controlled over serial. When the motors are hooked directly to the speed controller all four motors work, however when the motors are connected through longer wires they do not seem to work.

For the setup with the longer wires (which we have to use in the final product): The ends of the motors are currently connected through solder and seal connectors to the long wires connected to the speed controller. Three of the four motors work, but one motor does not. It emits four rumble sounds and then a beep. Photos are attached of the setup, and a video is attached of the not-working motor making its noises.

Would appreciate any help on this,

Video link:

Hi @LittlejohnVMI,

Significantly extending the wire length between an ESC and thruster can cause various issues, an is not normally recommended. The ESC and thruster behave as a single unit, and significantly longer wires increase the noise the noise between them, which may affect proper commutation and thus operation of the thruster.

Keeping the ESCs close to the thrusters, and then controlling the ESCs at a distance over serial/network interface is usually preferred.

It looks like the one thruster is not starting up properly. What length/gauge of wire are you using? Thin and long wire with high resistance will cause excessive voltage drop, and the thruster may not be receiving enough power to run properly. This could also be caused by a mismatch in resistance of the thee phase wires- make sure all three wires and connections going to each thruster are as close in resistance to each other as possible, check with a milliohm meter or sensitive multimeter if you can.


Hi, thanks for the response. I’m a little confused as the other three motors are working with the same gauge and length of wire. The wire is 0.04 inches wide (18 gauge) and is around 27 inches from motor to the speed controller.

We fed nine wires through to the motor area, in sets of three but are only using two motors (6 wires). We are now going to try using the last set of three to control the problematic motor. Would appreciate any other advice,


Hi @LittlejohnVMI,

I’m not quite sure I understand-

These statements appear contradictory? My understanding is that the thruster operated nominally when hooked up directly to the ESC, but not when using the extension, is this not the case?

In any case, thanks for confirming the length an gauge, I previously assumed your setup involved running the phase wires along the whole length of the tether.

My suggestion would be to check your connections, and swap ESC/thruster pairs along the wires to better determine the problematic element.