Noise in the engine

I have a problem with a wheel. the right motor of my robot doesn’t work, I tried to recheck all the wiring but it didn’t solve the problem. When I reversed the two wheels the problem moved to the new wheel so I think it’s a motherboard problem. I’ll explain better, the engine makes a strange noise as if a phase wasn’t working. When I try to make the robot move with the joystick it turns on itself the robot understands that it is not going forward but rotating: in fact in rviz simulation the robot rotates on itself. The blocked engine in the meantime makes a bit of noise but if it is touched it immediately tries to recover the rpm it has lost. with the oscillator I measured the high and low voltage levels of the FAN7389 but on the blocked motor the levels are quite low. I can’t identify the problem, could you please help me?

I don’t know if it ever worked for you and then broke or recently stopped working. We run a final test at the factory to verify motor and MCB operation.

When you say ‘right wheel’ we usually give sides of the robot relative to as if you were sitting in the seat of the robot looking forward (over the power switches). The Right side is then opposite where the camera mounting is done.

Since this follows the motherboard let me suggest that the most common problem is the wiring of one or more of the wires from the side of the cable that is zip-tied to the mother board. I will assume you have unplugged in motor and switched them that way so the part of the cable attached to the MCB remained the same, that is to say cable attached to right screw terminals.

The motor cables on boards since MCB rev 5.2 have been very clearly labeled with the proper wire colors. Suggest that you look at each of the 9 total colored wires where big ones go to 3-pin terminal and from top down are Yellow, Green, Blue. Convince yourself that they are held well AND that the terminal connections press on bare wire and are not for some reason just pressing on wire insulation. This is almost always the sort of issue although it is of course possible one of the components has broken that is almost never the case so verify connections first please.

I hope this helps, Mark

Thank you for your prompt response and for your suggestions regarding the issue I’m facing with my Ubiquity robot.

To clarify, the problem with the right motor has recently occurred; the robot was working correctly before this issue arose.

I appreciate your clarification regarding the side terminology, and you are correct; I was referring to the side opposite to where the camera mounting is done.

Regarding your suggestions, I did indeed unplug the motors and swapped them, keeping the part of the cable attached to the MCB the same, as you mentioned.

I have now reviewed the motor cables and the terminal connections as per your guidance. The cables on my MCB (revision 4.9) are clearly labeled with the proper wire colors. I have ensured that the wires are securely held, and the terminal connections are pressing on the bare wires without any issues with insulation.

Your insights are incredibly valuable, and I’m grateful for your assistance. I followed your advice and rechecked the connections to ensure everything is in order. However, despite these checks, the problem persists.

I was wondering if you could kindly suggest further steps or procedures to identify and address this issue more comprehensively. I would greatly appreciate receiving additional guidance from you.

Thank you again for your invaluable assistance.

I would then agree it is a problem on the motherboard. We have not specifically ruled some internal short cable failure but we have never actually had the cable itself fail, just connections to motherboard or motherboard itself. Since your issue did not happen due to a recent wheel cable unplug/plugin it would be most likely not the cable itself. Anything is possible of course.

Please send an email to
In this email include the serial number of the Magni itself which is supposed to be on a sticker on the bottom side of the magni.
Also include the serial number of the MCB (Motherboard as you are calling it). This is supposed to be on a white sticker and easy to read from the top of the board.

Send this email from your email so a reply can get back to you.

In the subject put ATTN Mark and also say Wheel replacement in the subject please.