I made a USB fan to cool down my Raspberry Pi 3, (it had heating problems). I supplied power to the fan from another battery while it was plugged into the USB port.

since then it has not been working...

when I plug in the HDMI cable the Pi appears to boot for a second and turns off, it boots again and turns off..

after sometime... the raspberry pi is booting but any of the USB ports are not working I don't think there's anything wrong with the USB IC as it is the same as the Ethernet IC but the Ethernet still works

What is the problem?

  • 1
    Seems like a current overload...? I would not use the HDMI after those traumatic experiences in my TV...I would call it a day, and would buy a new board. May 15, 2016 at 9:42
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    "I don't think there's anything wrong with the USB IC as it is the same as the Ethernet IC but the Ethernet still works" == "I don't think there is anything wrong with my car as the air conditioner still works, therefore obviously the whole car must be ok. So why do the brakes fail?". Maybe an actual mechanic could provide a better hypothesis here.
    – goldilocks
    May 15, 2016 at 11:23
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    I tried formatting the SD card but still got no good results... the usb ports had got damaged so I got a new board as one of you suggested
    – DS3a
    May 18, 2016 at 11:02
  • Electic motors have bad habit of producing voltage spikes. Sometimes there is some protection by adding a diode and a capacitor. If this was some very cheap fan it could be that some voltage spike (this also means current spike) damaged your RPI. Jan 25, 2017 at 11:41

2 Answers 2


My first option would be to check the SD card. In my experience those normally just go first and give multiple sorts of issues there after. I would assume that if it was anything then the pi would not go on at all.

However you can have a look at this guide to try diagnose if it is a power related issue with the pi.

Power start-up Troubleshooting

If not the issue maybe have a look at other SD card related posts that might help you. Hope one of these helps you.

Corrupt SD Card

Element14 post on dead pi


I don't think the Pi has enough power to supply the fan. Most people use USB Powered hubs to power high power USB devices like hard drives about/above 100 GB. Or you can switch the USB cable with a actual power plug, but that might be too much work. To make it simple I would get a hub to power it, or power it by another nearby USB device.

Pi's are powered by 5 volts, and your fan may take up more than 5 volts.

The Pi is probably gaining a bit of power on startup but then loses it when it realizes that it has to power the fan. Then it shutdown because of loss of power and repeats.

Hope this helps, Dallin

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