Brain will not connect to controller

The brain will show the tether icon when controller is connected with blue cable and when disconnect it does no go to searching mode to connect the controller… Any suggestions… Firmware and controller are up to date and I have tried switching out radios

One of our teams had this issue because the radio was not pushed all the way in. Probably not you are experiencing, but worth checking. It will not come out easily if all the way in.

Very True jrp62,
Whether it be the radio or the controller pushing the radio all the way in usually the key. I’m always afraid of breaking things so I’m pretty careful pushing these things in. When the robot doesn’t connect I let one of our fearless kids push the radios in. Full strength and “Pop” it goes in. It takes a bit of effort to seat these radios all the way down.


Hi James,

We’re sorry that you have had encountered this issue. The most likely cause of this issue is that the radio is not plugged in all the way in either the Robot Brain or the Controller. When the Radio is plugged in all the way, there should only be 7-8mm of it visible. If you push and hold the red Radio Release button on the bottom of the Robot Brain, it will make it easier to both insert and remove radios. You must remove the battery from the Controller to insert and remove Radios.

The reason that the Robot Brain has this button, as well as the reason why you cannot remove the Radio from the Controller without removing the battery, is so that if a Controller is dropped or a robot is jostled in a competition or classroom environment, the radio connection remains connected.

If you only notice the radio connection dropping when you are starting your custom program (from either ROBOTC or Modkit for VEX), this is likely because your custom-program is set as autonomous-only. In autonomous-only custom programs, the Radio connection is disabled as soon as the program starts, even if a Controller was previously connected. The reason for this, is so that at large VEX IQ Challenge competitions, teams running Programming Skills matches do not use up radio channels that might be needed by teams in Robot Skills or Teamwork Skills matches.

If you have any additional questions or comments, please feel free to contact our technical support folks at or by calling +1-903-453-0802.


  • Art