When I attempt to turn on my bluetooth, the response on the display after about 5 seconds is "Failed!" Then I'm sent back to the main menu.

I've reset the unit and updated to latest firmware (1.31) to no avail.

I'm curious about the "doomsday" button on the inside of the battery compartment--you have to remove a battery to push it (thus the unit is not powered up if you push it by accident), so it obviously could cause significant issues if it is pressed. I am an electronics tech--I know what to do to power it up and press the button, but there is no reference to what it is there for, so the little voice of reason says, "don't."



  • As I understand it, your question is more "What does the hidden button under the NXT battery?" rather than the bluetooth issue - is that correct?
    – Joubarc
    Apr 21, 2013 at 10:23

1 Answer 1


The hidden button under the NXT battery seems to be a reset button, which has to be pressed for 7 seconds to have any effects. I assume it resets the brick in its factory condition, but I didn't find any specific documentation from LEGO on it.

However, there was an issue a few years back which caused the brick to freeze and click permanently (which was called the "NXT Click of Death"); and the solution included a hard reset using that button. (It's just one out of many pages on the subject, by the way)

Will this solve your Bluetooth issue? I don't know. If there's a problem with your firmware, then it's possible, since you'll need to reflash one anyway (since it will be reset to factory settings). Maybe trying alternate firmwares might shed some light on your brick's condition, too.

If that doesn't solve it, I would advise to contact the mindstorms customer support - worst case scenario, they establish your NXT brick is indeed defective, and they'll probably provide you a replacement.

  • So, I guess it is a "master reset" which is on a deeper level than the "technic reset button." I will give it a shot and let you know if it helped. Otherwise, I suspect there is an issue with my bluetooth card. Obviously, it is on a microprocessor-to-bluetooth chip issue as it will not function on a level that would indicate that the micro is able to configure the bluetooth chip. Thanks! I really appreciate the assistance.
    – lamafozzy
    Apr 22, 2013 at 3:03
  • BTW: I am not talking about the reset button through the mounting hole under the USB port. There is another button inside the battery compartment that is only accessible if you remove one of the batteries. I just read one of the links you posted and it suggested that the trick is to use the reset button I referred to as the button in the "Technic hole" in the manual on pg. 60. Tried that--it didn't work. There is no reference to the button I'm talking about in the manual and so I figure it is "Bad Juju" to press it unless I know exactly what it does.
    – lamafozzy
    Apr 22, 2013 at 3:22
  • Well, on the other hand LEGO usually doesn't put any "bad juju" in its toys - they're meant to be safe for kids after all. So even if it, erm, bricked your brick, you'd probably still be able to get a replacement. But if you're in doubt, then by all means, contact the customer service first.
    – Joubarc
    Apr 22, 2013 at 6:49
  • 2
    No, the button located under the battery pack is there to make the brick know that it is powered by a rechargeable battery pack. The battery pack has a pin that presses this button, this changes the battery charge level voltage thresholds to adapt to different technology.
    – Philo
    Apr 22, 2013 at 12:25
  • 1
    Well, thank Philo, I feel his comment is more useful than my answer anyway (Philo, feel free to write a full answer of your own)
    – Joubarc
    Apr 23, 2013 at 6:51

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