Internal drive stopped working, but will boot externally.

[thingstoponder]

I've run into an odd problem. My computer froze so I did a hard reset and on reboot I got the dreaded question mark icon. I went into disk utility and the drive was still visible so I figured the internal drive adapter wasn't dead.

Anyways, I opened up the machine and took the drive out assuming it was dead. Just as a last resort I plugged the drive into an external drive adapter and it booted right into the OS no problem and I'm using it right now.

Anyone have any idea what's going on? I'm currently backing up my last files. I can try and put it back inside the macbook and do a fresh install if necessary.

 

[Hellhammer]

It could be a failed SATA cable, but try putting it back inside first. You should also try SMC/PRAM resets as well as making sure that the internal drive is selected as a startup volume.

 

[Fishrrman]

OP:

If it's a MacBook Pro, the internal SATA ribbon cable can "get flaky" sometimes. The results would be very much like you report above: internal drive won't work, but take the drive out, connect it via an external source (such as USB) and it then boots and runs fine.

Solution is to replace the internal ribbon cable, they're not expensive.
You already know how to "get inside", obviously.

Final suggestion:
Get an SSD along with the new SATA cable, and put that inside.
GREAT speed improvements.

I'd recommend either Crucial or Sandisk as a source for the SSD.