MacBook Pro 13" Troubleshooting

devitol

Hi John,
It's been a while since I posted. I've started working with the 2011 i5 models recently and noticed that many seem to come my way that have the same issue: when power is supplied to the board the fan spins and else nothing happens (chime, POST, etc) or the fan spins and then stops and then spins and then stops. I know that usually once power is given to the board through AC and battery, the i5s tend to startup on their own, but I have come across any Core 2 Duo models that exhibit the spin and stop, spin and stop issue. Have you had any luck figuring out what could be going on with these boards?

As always, that you for your insights and expertise.

John

Hi Devitol! Thanks for the post.

Unfortunately I don't get a lot of new-ish machines, so you're way ahead of me in terms of experience with i5s.

I've found several white unibody machines with a sticky power button, and since the power button is effectively permanently pressed in, these machines do the equivalent of PMU/SMC resets repeatedly, which includes the fan running on high for a few seconds every time they reboot, and that sounds roughly equivalent to what you are experiencing (fan on high, then pause, then fan on high). You might try disconnecting the keyboard/power ribbon cable entirely and see if you get a different result from powering on by triggering the power-on pads. If it works fine that way, you know it was a stuck button, and you can then open up and clean out the power button mechanism. If it still doesn't work, you've ruled out the topcase/keyboard/power button as the issue.

In terms of generic advice, I would try to reset the PMU/SMC (while off, hold in the power button until you hear a tone), reset the PRAM, examine the board for corrosion that you can clean off, and test the RAM slots one at a time by powering on with one slot empty, and then the other.

The 1.2GHZ 12" iBook G4 commonly had a "fan on high" issue, but that was due to the loose connection of a pin on a chip on the underside of the board, so I doubt there's anything to be learned from that. That was also a continuous fan, with no pause.

I have a hunch about the sticky power button though...let me know if that solves it! With the white unibodies it's a very common issue, and easily fixable with a new topcase. It would be pretty cool if i5s had the same flaw and were also that easy to fix (and potentially easier, since with Pros you can disassemble and work on the power button assembly, unlike with white unibodies topcases, which are molded together).

Forgot to ask, does the screen turn white at all, or is it always black? Do you hear a solid tone like you would during a PMU/SMC reset? Does the sleep light turn on, or flicker?

Good luck!

John