Problem with USB Port - ¿Is it on short circuit?

Well, here's the problem: If i connect my Arduino Mega to my PC or MAC both deactivate the USB port saying the USB device is consuming too much power.

Is there anything I can do to find out what's the problem with my Arduino?

If I connect to 12V with the other input it works perfectly.

If I measure resistance between GND and 5V USB input I get 30ohms ... is a correct value??

Thanks in advance for any assistance.

30 ohms to ground? No, that's not correct, something is damaged. But that is a very crude thing to measure.

You say it works at 12v - do you mean that USB communication works when it's powered by 12v external, or just that whatever you had on there before runs?

What serial adapter does your board have? (check the markings on the chip next to the USB - official and faithful clones will have a 16u2, other clones will have CH340G or FT232 serial adapters.)

When powered on 12v, feel if any IC's on the board are getting hot.

DrAzzy: You say it works at 12v - do you mean that USB communication works when it's powered by 12v external, or just that whatever you had on there before runs?

I mean that the program i had on there before runs ok. If i connect to pc it gives to me the "consuming too much power" error.

DrAzzy: What serial adapter does your board have? (check the markings on the chip next to the USB - official and faithful clones will have a 16u2, other clones will have CH340G or FT232 serial adapters.)

It have a 16u2.

DrAzzy: When powered on 12v, feel if any IC's on the board are getting hot.

Nothing seems to be warming...

Any idea? can i test some component with a multimeter? which one is the suggested? If the problem is with the 16u2, i have to start thinking in a new arduino right?

The error message you are seeing is usually seen on notebooks and laptops. It means that the USB ports cannot supply enough power to the USB device.

If this is the case then a POWERED USB HUB of good quality would be a good purchase.

If you are seeing this on a desktop computer then you may be using an UNPOWERED HUB in which case the same answer is to purchase a POWERED hub.

Alternative is to supply the Arduino with its own power from another source and use the USB only to program it

Solved. Unweld the USB port, weld it again and it's working again. Do not ask why.

Greetings, thanks for the help.